Giovanni della Porta, the Renaissance scholar who encrypted messages inside eggs to fool the Inquisition

Giovanni Battista della Porta was born in November 1535 in Vico Equense, a municipality of the Kingdom of Naples that since 1504, by the Treaty of Lyon, belonged to the Crown of Aragon and with the rise to the throne of Joanna the Mad was transformed into a viceroyalty, remaining in Spanish possession until 1704. Giambattista, as he was usually called, was the third son of a noble family, which allowed him to receive an exquisite education, increased because his father, Nardo Antonio della Porta, had always shown great eagerness for knowledge.

Current view of Vico Equense / Image: Valerio Capello on Wikimedia Commons

Therefore, his house was frequented by artists, philosophers and people of culture, who not only generated an environment conducive to the education of children but some even served as teachers and tutors. It was the embodiment of that famous Renaissance spirit, born precisely in Italy, which sought a broad and complete knowledge in all fields and whose maximum expression was Leonardo da Vinci. The wealthy classes incorporated this concept into their lives by identifying it with the ideal of the perfect gentleman, and its members learned singing, dancing, poetry, mathematics, philosophy and classical languages, as well as horsemanship and the skill of weapons.

Cover of a 1589 edition of Magiae naturalis / Image: public domain on Wikimedia Commons

The Della Porta became a model. Although they studied music at the Scuola di Pitagora, it was in science that they really stood out, and more specifically Giovanni did so in mathematics and engineering, writing his first texts at the age of fifteen. It’s not that he dedicated himself exclusively to them, since he demonstrated a literary talent and published almost fifty plays, including dramas, comedies, tragedies and even liturgical pieces (all of them written not in the prevailing style of commedia dell’arte but in another more cultured style called commedia erudita). But his literary merits remain today in the shadow of contemporaries such as Machiavelli, Balthasar de Castiglione, Ludovico Ariosto or Torquato Tasso and there are other things that interest us about him.

His research work has led to important technological advances in various fields, from the military to the agronomy, astronomy, optics, meteorology, etc. The result was the invention of a hydraulic system and the manufacture of various instruments, of which we should highlight the improvement of the camera obscura and the magic lantern, invented respectively by the Muslim Ibn al-Haytham and the German Jesuit Athanasius Kircher, describing their experiences in this regard in a 1558 treatise entitled Magiae naturalis (in which, by the way, he also spoke about invisible ink).

Also, in 1586, he published De humana physiognomonia, in which he added to the interest aroused by the anatomy and biology of Man in his time. In that line he was also the author of a botanical treatise, Phytognomonica, in which he reviewed for the first time his studies on fungi, opening the way to mycology. It should be added that he could have made the first telescope, although there is no way of knowing for sure because the book where he explained it, De telescopiis, remained unfinished at his death, leaving the fame for his contemporaries such as Hans Lippershey and Galileo Galilei.

Pages from De humana physiognomonia/Image: public domain on Wikimedia Commons

As he had established his own museum at home, in 1560 he founded the Academia Secretorum Naturae (Academy of Nature’s Secrets), considered one of the first scientific societies and whose members were self-appointed otiosi (idle), having to present some natural discovery in order to join. This was too suspicious for the Inquisition, which opened a process because the investigations about alchemy and the search for the philosopher’s stone, although then part of Science, were often considered on the verge of occultism.

Della Porta was finally exculpated, since his religiosity was so much in evidence that he would become a lay brother of the Society of Jesus. But one thing was the person and another the institution, which continued to raise suspicion, hence in 1578 Pope Gregory XIII ordered him to terminate it. It was substituted by the Accademia dei Lincei, founded in the Palazzo Corsini in Rome (the same where Queen Christina of Sweden would reside) by the naturalist Federico Cesi and whose most illustrious member, apart from Della Porta, was Galileo (as he was also prosecuted by the Holy Office and the academy supported him, it ended up being dissolved).

Palazzo Corsini in Roma / Image: public domain on Wikimedia Commons

To conclude, we only need to talk about the Neapolitan scholar’s works on ciphers, a subject in which he is considered the great reference of his time. His knowledge in this respect is reflected in titles such as De furtivis literarum notis, Taumatologia e criptologia and De occultis literarum notis. In the first one he introduced the first documented concept of substitution cipher, a method in which text units, either letters or groups of them, are substituted in a more or less complex way, assigning each sign a different one but keeping the order of the whole. In its most advanced version, substitution ciphering was used by the Germans in World War II with their Enigma machine.

A key encrypted in the De furtivis literarum notis / Image: public domain on Wikimedia Commons

But there is no doubt that the most amazing thing in this matter is what we mentioned at the beginning of the article, the method devised by Della Porta to write messages hidden inside eggs. The irony is that the Inquisition played a key role in this, as it had imprisoned several of his colleagues from the Academia Secretorum Naturae to put them on trial, and the only way the Neapolitan found to communicate with them – since prisoners in such circumstances were isolated from all contact – was to send them written messages through food. Now, this was meticulously checked by the guards and there was only one thing that could pass unscathed: the eggs.

How did he take advantage of them? By using a special ink that he made with vegetable pigments and alum (an aluminum sulfate that crystallizes in water and serves as a fixative). Della Porta would write on the shell, which, being semi-porous, would allow the ink to penetrate. Once it dried, the egg was boiled and the hot water erased the writing on the outside but not on the inside, so that the prisoner could break the shell and read the message printed on the white.

In spite of being exculpated, Della Porta continued to have problems with the Inquisition and seeing many of his books censored, probably because of his friendly relationship with Paolo Sarpi, a religious of the order of the Servants of Mary, a theologian but also a scientist, who earned the enmity of Paul V by defending the interests of Venice before him (and who would be excommunicated for promulgating the separation of the Venetian Church from that of Rome and would even suffer a serious assault). In 1598, however, this uncomfortable situation ended and he was able to work in peace, although dedicated to writing plays, until his death in Naples in 1615.


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