"The Voynich manuscript is a mysterious illustrated book written in an indecipherable text. It is thought to have been written between approximately 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."
Scans of the book on Flickr