In September 1561, a slim octavo volume rolled off Giovanni Bariletto’s press in Venice. Its full title promised “cose minerali, medicinali, arteficiose, & alchimiche” plus the “arte profumatoria, appartenenti a ogni gran signora”: minerals, medicines, crafts, alchemy, and perfumery for every great lady. The author named on the title page was Isabella Cortese. The book, I secreti della signora Isabella Cortese, contained roughly 300 recipes that taught readers how to cure plague, temper steel, transmute metals, remove stains, whiten teeth, dye hair, distill perfumed waters, and produce the philosopher’s stone. It was addressed, explicitly and unusually, to women.
Within four decades, the book had gone through at least seven editions. By 1677, printers were still resetting it. Two German translations appeared in the 1590s. Tommaso Garzoni cataloged its author among the professori di secreti, the only woman in the category. Whether “Isabella Cortese” was a real woman, a composite persona, or a marketing invention remains, after more than four and a half centuries, genuinely unknown.
What “Secrets” Meant
A modern reader seeing the title assumes mystery, occultism, hidden knowledge. The sixteenth-century meaning was different. A secreto was a proven experiment, a tested recipe, the hidden virtue embedded in nature waiting to be unlocked through correct technique. The Latin root carried connotations of “set apart” rather than “concealed.” When Cortese promised secrets, she was promising what worked.
The genre these books belonged to, the libri di secreti, had been growing since the mid-fifteenth century, but it exploded in 1555 when a book called I secreti del reverendo donno Alessio Piemontese appeared in Venice. The supposed author, a pious old man named Alessio, was actually Girolamo Ruscelli, a professional writer who claimed the recipes had been tested by his Accademia Segreta in Naples, where each procedure required three successful trials before inclusion. Whatever the truth of that claim, the book was a phenomenon: over fifty European editions by century’s end, translated into at least six languages, and eventually exceeding 100 editions across its full publication history through the 1790s. Ruscelli had proven that practical knowledge, written in vernacular Italian rather than scholarly Latin, sold.
Cortese’s Secreti arrived six years into this boom. But where Ruscelli wrote as a pious male scholar deferring to ancient authorities, Cortese wrote as a woman who had traveled, tested, and dismissed the old masters. The angle was different. The market was ready.
The Voice in the Preface
Almost everything we know about Cortese as a person comes from the book’s dedicatory letter, addressed to her brother Mario Caboga, identified as the Archdeacon of Ragusa (modern Dubrovnik). Caboga was a real person. He taught at the University of Padua, belonged to the Accademia dei Confusi in Viterbo, and was himself an avid but apparently unsuccessful alchemist. He died in 1582.
In the letter, Cortese tells her brother to stop wasting his time. She has studied alchemy for over thirty years, she says, including the works of Geber, Ramon Llull, and Arnold of Villanova. Her verdict is devastating: they recorded nothing truthful in their books, only images and puzzles. She wasted time and “almost lost my life and all my possessions” following their instructions. Instead, she has traveled through Hungary, Moravia, and Poland, gathering practical secrets that actually work. She now writes them down for her brother, with instructions to follow her procedures exactly: “do what I tell you and write for you.”
This is a remarkable rhetorical performance. A woman dismissing the entire Latin alchemical canon, the accumulated authority of centuries, on the grounds that she has tested it and it failed. Whether the voice belongs to a historical Isabella Cortese or to a skilful fiction, the posture is the same: experience over authority, the furnace over the library.
What the Book Contains
The Secreti is organized into four books, each addressing a different domain.
Book One: Medicine. Approximately thirty recipes for plague remedies (contra peste & veneno), syphilis pills (contra il mal francese), antidotes against poison, wound-healing ointments, treatments for ringworm (tigna) and scrofula, and recipes to help women recover after childbirth. The syphilis treatments likely involved mercury compounds, which were the standard therapy of the era, dangerous and sometimes effective.
Book Two: Alchemy and Metallurgy. This section opens with a set of practical rules for the aspiring alchemist, then proceeds to transmutation of metals, the preparation of sulfuric acid, philosophical mercury, potable gold, and the philosopher’s stone. The metallurgical recipes include gilding, tempering steel, and casting and coloring metals. The rules themselves are a kind of survival guide.
Book Three: Practical Arts. Dyes, fabric care, stain removal, ink-making, soap, candles, crystals, mirrors. The household-to-workshop bridge.
Book Four: Perfumery and Cosmetics. The longest section, with 221 formulas. Teeth whiteners, creams, hair dyes, lip color, perfumed waters, face whitening preparations (including lead-based concoctions), and the belletti (cosmetics). The history of perfumery runs much deeper than most people realize, and Cortese’s arte profumatoria sits directly in that tradition. One recipe calls for white-feathered pigeons fed exclusively on pine nuts for eight to fifteen days, then butchered and distilled with sweetened bread, silver, gold ducats, and goat’s milk. The resulting water was applied to the face for a luminous complexion. Another promises that “nessun potra conoscere che habbi messo il belletto”: nobody will know you are wearing makeup.
That last detail matters. Renaissance women were expected to enhance their appearance but conceal the evidence. Cortese’s cosmetics recipes were tools of social performance as much as chemistry.
The Ten Rules
Before the alchemical recipes in Book Two, Cortese lays down rules of practice. They read less like scientific method and more like operational security for a solo practitioner working with dangerous materials in a culture that prosecuted witchcraft.
Work alone. Keep your laboratory secret. Master your vessels and your fire. Find a trusted servant but never leave them unsupervised. If anyone asks, deny your expertise. Never teach the Art to anyone, because revealing the secret causes it to lose its efficacy. Use sturdy equipment made of terracotta or glass. When you succeed, thank God and give to the poor.
And then the most dramatic instruction: when you have learned everything in this book, destroy it.
The command to burn the book after mastering its contents serves multiple purposes. It protects the reader from discovery. It preserves the scarcity that gives secrets their value. And, for a publisher, it is spectacularly good marketing: you are holding something so valuable that the author wants it to exist only in your hands.
For a woman working with mercury, sulfur, and fire in sixteenth-century Venice, the rules had an additional urgency. The line between respected practitioner and suspected witch was thin. Discretion was not merely prudent. It could be life-saving.
The Authorship Puzzle
Here is where the story becomes genuinely strange. No archival record of a person named Isabella Cortese has ever been found outside the book itself. No baptismal certificate, no marriage contract, no will, no letter, no contemporary reference. The dedicatee Mario Caboga is documented. The printer Giovanni Bariletto is documented. The privilege holder Curtio Troiano di Navo, Bariletto’s brother-in-law, is documented. But the author is a ghost.
Several pieces of circumstantial evidence deepen the puzzle.
First, “Cortese” is an anagram of “secreto.” The name also means “courteous” or “courtly” in Italian, fitting the book’s address to noblewomen. Either reading suggests construction rather than biography.
Second, in the same year, from the same press, with the same printer’s device, dedicated to the same Mario Caboga, with the privilege held by the same Curtio Troiano di Navo, Bariletto published a second book of secrets: Timoteo Rossello’s Della summa de’ secreti universali. Both books share identical recipes, including a “universal medicine” (camphor, quicksilver, and sulfur) and an erectile dysfunction remedy (quail testicles, winged ants, amber, musk, and elder oil). The overlap is too specific to be coincidence.
Third, six years earlier, Ruscelli had published his phenomenally successful Secreti under the pseudonym “Alessio Piemontese.” The books-of-secrets market was already established as a genre where pseudonyms were not exceptions but standard practice.
Meredith Ray, whose Daughters of Alchemy (Harvard University Press, 2015) provides the most thorough scholarly treatment, keeps the question genuinely open. Cortese might be a real woman whose archival traces have simply not survived, which is common for women of the period. She might be a pseudonym adopted by a male compiler (Ruscelli himself has been suggested) to reach the women’s market. She might be a collective persona, a name attached to a compilation assembled by multiple hands. The honest answer is: we do not know.
What we do know is that the text performs something specific regardless of who wrote it. It centers female readership. It addresses women as experimenters. It furnishes them with tools. Whether the voice belonged to a woman named Isabella or not, the effect on readers was the same.
The Venetian Printing Machine
The book’s success is inseparable from its place of origin. Venice in the 1560s was the undisputed capital of European printing. Over 250 publishers operated there, producing more than 27,000 editions across the sixteenth century, roughly half of all European print output. The city’s trade routes provided distribution across the continent. Its spice trade supplied the exotic ingredients the recipes called for. And compared to Rome, Venice was relatively liberal about censorship, which drove printers southward from the Papal States.
The Secreti first appeared in 1561 from Bariletto’s press. Confirmed editions followed in 1565, 1574, 1584, 1588, 1595, and 1603, seven editions within forty-two years. Reprints continued through the seventeenth century: 1614, 1619, 1625 (from Lucio Spineda), 1642, 1662, and 1665 (from Carlo Conzatti, who described it as the fifteenth edition). A final known Italian edition appeared in 1677. Two German translations were published: Hamburg in 1592 and Frankfurt in 1596.
This is a publication span of 116 years. Readers did not just buy the book. They used it, copied from it, passed it on. The Secreti was not a curiosity. It was a working manual.
Three Books, One Network
Cortese’s Secreti did not exist in isolation. It was one node in a network of books-of-secrets publications that defined a new kind of knowledge market.
Ruscelli’s Secreti del reverendo donno Alessio Piemontese (1555) was the category founder, the mega-bestseller. Giambattista della Porta’s Magia Naturalis (1558, expanded to twenty books by 1589) provided the genre’s intellectual framework, defining natural magic as the manipulation of natural properties through practical technique rather than supernatural invocation. Della Porta founded the Accademia dei Segreti in Naples, where admission required demonstrating an original experimental discovery. Leonardo Fioravanti’s Del compendio de i secreti rationali (1564) added the voice of the itinerant empiric, the medical school dropout who learned from peasants, shepherds, and wise women. Giovanventura Rosetti’s Notandissimi secreti de l’arte profumatoria (1555) was the first dedicated treatise on perfume-making.
And behind the scenes, there were the manuscript collections that never reached print. Caterina Sforza, Countess of Imola and Forli, compiled 454 recipes across medicine, cosmetics, and alchemy in her Gli Experimenti in the late fifteenth century. They remained unpublished until 1893. Their value, like all alchemical knowledge, lay precisely in their scarcity.
Cortese occupied a unique position in this landscape. She was the only woman whose name appeared on a printed, commercially successful secrets book. Hildegard of Bingen had written about natural philosophy and medicine three centuries earlier, but in Latin, for monastic audiences. Cortese wrote in Italian, for the market, and she sold.
The Professoressa di Secreti
In 1585, the Augustinian monk Tommaso Garzoni published La piazza universale di tutte le professioni del mondo, an encyclopedic catalog of over 500 professions. Among them he listed the professori di secreti: people who searched for things “whose reasons are not so clear that they might be known by everyone, but by their very nature manifested only to a few.” These were not university professors. They were practitioners who claimed authority through experiment rather than credentials: recipe authors, itinerant healers, court alchemists, academy members.
Garzoni listed Isabella Cortese as the only woman among them.
The category itself reveals something about the knowledge economy of the late Renaissance. The professori di secreti occupied an ambiguous social space. They were not charlatans (though their enemies called them that). They were not formal scholars (though some had university training). They were something new: a professional class defined by practical know-how and its commercial distribution through print. The printing press had created a market for knowledge that had previously circulated only through guilds, courts, and personal networks. The books of secrets were the product of that market.
What Cortese’s Book Means Now
The Secreti is not a forgotten curiosity. It is an early document of something we are still working out: the relationship between practical knowledge, authority, gender, and public access.
Cortese’s cosmetics recipes taught women chemistry through beauty. Her medical recipes gave them tools to manage health outside the physician’s consulting room. Her alchemical rules taught operational thinking: control your fire, trust your equipment, protect your knowledge. The book did not merely inform. It equipped.
The authorship question, far from diminishing the book, makes it more interesting. If Cortese was real, she was a woman who dismissed the entire Latin alchemical tradition and replaced it with her own tested procedures, an act of intellectual courage in a period that burned people for less. If she was a fiction, she was a fiction that someone in the Venetian publishing world thought would sell, which means the market was ready for a woman’s authority in experimental knowledge. Either way, the book performed the same cultural work: it told women they could experiment, and it gave them the recipes to do it.
The 1561 first edition survives in the Wellcome Collection in London. The 1565 edition is digitized at the Getty Research Institute. Anyone can read it. The secrets are no longer secret. But the questions they raise, about who gets to produce knowledge, who gets to publish it, and whose name goes on the cover, have not been settled yet.
Sources
Bibliography. The same list is held in the article’s frontmatter for the citation tools that read it programmatically.
- Cortese, Isabella. I Secreti della Signora Isabella Cortese, ne’ quali si contengono cose minerali, medicinali, arteficiose, & alchimiche, & molte de l’arte profumatoria, appartenenti a ogni gran Signora. Venice: Giovanni Bariletto, 1561
- Ray, Meredith K. Daughters of Alchemy: Women and Scientific Culture in Early Modern Italy. Cambridge, MA: Harvard University Press, 2015
- Eamon, William. Science and the Secrets of Nature: Books of Secrets in Medieval and Early Modern Culture. Princeton: Princeton University Press, 1994
- Ray, Meredith K. ‘Experiments with Alchemy: Caterina Sforza in Early Modern Scientific Culture.’ In Gender, Authorship, and Early Modern Women’s Collaboration, edited by Patricia Pender. London: Palgrave Macmillan, 2017
- Sforza, Caterina. Experimenti de la Ex.ma S.ra Caterina da Furlj Matre de lo Inllux.mo Signor Giovanni de Medici. Manuscript, c. 1500-1509. Edited by Pier Desiderio Pasolini in Caterina Sforza, vol. 3. Rome: Ermanno Loescher, 1893
- Eamon, William. ‘How to Read a Book of Secrets.’ In Secrets and Knowledge in Medicine and Science, 1500-1800, edited by Elaine Leong and Alisha Rankin, 23-46. Farnham: Ashgate, 2011
- Piemontese, Alessio (Girolamo Ruscelli). De’ Secreti del Reverendo Donno Alessio Piemontese. Venice: Sigismondo Bordogna, 1555
- Ray, Meredith K. ‘Letters from the Cloister: Learned Women and the Italian Renaissance Convent.’ MLN 124, no. 1 (2009): 121-138
- Park, Katharine. Secrets of Women: Gender, Generation, and the Origins of Human Dissection. New York: Zone Books, 2006
- Leong, Elaine, and Alisha Rankin, eds. Secrets and Knowledge in Medicine and Science, 1500-1800. Farnham: Ashgate, 2011
- Strocchia, Sharon T. Forgotten Healers: Women and the Pursuit of Health in Late Renaissance Italy. Cambridge, MA: Harvard University Press, 2019
- Findlen, Paula. ‘Translating the New Science: Women and the Circulation of Knowledge in Enlightenment Italy.’ Configurations 3, no. 2 (1995): 167-206
- Bell, Rudolph M. How to Do It: Guides to Good Living for Renaissance Italians. Chicago: University of Chicago Press, 1999
- Nummedal, Tara. Alchemy and Authority in the Holy Roman Empire. Chicago: University of Chicago Press, 2007
- Pasolini, Pier Desiderio. Caterina Sforza. 3 vols. Rome: Ermanno Loescher, 1893
