Polygraphia is a cryptographic work written by Johannes Trithemius published in 1518 dedicated to the art of steganography.

[1] The full title is "Polygraphiae libri sex, Ioannis Trithemii abbatis Peapolitani, quondam Spanheimensis, ad Maximilianum Caesarem."

("Six books of polygraphy, by Johannes Trithemius, abbot at Würzburg, formerly at Spanheim, for the Emperor Maximilian.")

[2] It is composed of six books and a clavis (key): The work ends with alphabets of his invention as the "tetragramaticus" formed by 4 characters that are diversified in 24 letters and the "enagramaticus" of 9 characters and 28 letters, from which he gives examples of writings that belongs to something it resembles a natural language.

], both books, Steganographia and Polygraphia, are but a single work presented in two parts: the first is metaphysical and quite theoretical (it even hides a complete treatise on "angelology", or the study of angels with their names and hierarchies, between its pages), the second is more practical and is used for encoding messages.