While the books of secrets were basically recipes, in a practical sense, it is also true that the term "secret" long maintained a strong sense of a revelation of mysteries: either with the value of its disclosure, that is, to reveal knowledge reserved for scholars, or with the esoteric value of exploring the dark forces of nature. The subtitle of the work by Joshua Ferro in 1602 is explanatory. It is held in the Library of Pharmaceutical and Pharmacological Sciences of the University of Padova: "Treaty of marvellous secrets… Wonders which no one has known until today, nor could anyone write about them like the Author who has lived and experienced them and who shows it in everything he does, as the reader will come to understand" (digital copy). In the dedication to the Esteemed Mr Emilio Campolongo, professor of medicine at Padua and physician at the San Francesco Hospital , and in the prologue to readers, the author states that "they are Secrets gained through his own experience, pilgrimaging in various & diverse Regions with infinite toil" (c. A3v), that he feels obliged to share "even in a style a bit humble, and coarse" (c. A5r), now that he is "mortal, full of years and of diseases" (ibid), "knowing that the things that he will recount could not have been obvious to someone in many years" (c. A4v).

Among the countries visited in travels and in war, the author cites Peru, Panama, Jamaica, Cuba, Africa and the Indies. Real or imagined trips? It is only known that the author was counsel for Sephardic and Levantine Jews in Venice in 1607.

Some of the topics of the book are simply exotic: ambergris and its contested origins from whales, bezoar and its formation in the stomach of animals, pearls and how they are created, caught, sorted and used, precious metals and alchemy: "I will deal with the error that many make by saying that they grow metals of gold, of silver and precious stones, & all manner of metals which is false" (c. A6v). The work includes some exotic remedies, always cited in relation to healing experiences during the numerous incidents that occurred during the author’s travels, such as  "the fig tree from Hell called Mirasol”, “Stone of Holy Buga”, “Chinese Roots”, “Indian Sarsaparilla” and “what I could see of the animal called the Great Beast and its claws". Finally, he describes the "Cacaù" and the "Chocolate" (c. 114v), recently imported into Europe.

In closing, the author proposes sales, even to the "Clariss. Signori sopra la Sanità", that is, those who we now call the Venice health officials, of his own "Triaca": a theriac, or a drug with "admirable effect", prepared with "six things or simples ingredients" unobtainable in Europe and imported by him.