Balzac’s 1829 treatise La physiologie du mariage contains a strange passage:

“Four editions of the book, three of them printed in Balzac’s lifetime, in fact contain four different versions,” notes F.L. Bauer in Decrypted Secrets. “The author must have been playing a practical joke on the reader. Nevertheless, [French military cryptanalyst Étienne] Bazeries investigated such a cryptogram in 1901 and found that it did not fit any known scheme; it was une facétie de l’auteur.”