The Voynich manuscript is a mysterious illustrated book written in an indecipherable text. It is thought to have been written between 1450 and 1520. The author, script and language of the manuscript remain unknown... Over its recorded existence, the Voynich manuscript has been the object of intense study by many professional and amateur cryptographers, including some top American and British codebreakers of World War II fame (all of whom failed to decrypt a single word). This string of failures has turned the Voynich manuscript into a famous subject of historical cryptology, but it has also given weight to the theory that the book is simply an elaborate hoax — a meaningless sequence of arbitrary symbols.

The Codex Seraphinianus is a book written and illustrated by the Italian architect and industrial designer Luigi Serafini during thirty months, from 1976 to 1978. The book is approximately 360 pages long (depending on edition), and appears to be a visual encyclopedia of an unknown world, written in one of its languages, a thus-far undeciphered alphabetic writing.