Kryptographik

Kryptographik Lehrbuch der Geheimschreibekunst ("Cryptology: Instruction Book on the Art of Secret Writing") is an 1809 book on cryptography written by Johann Ludwig Klüber.
In 2011 the National Security Agency included a copy of "Kryptographik", used by a German cryptographer during World War II, as part of a 50,000 page release of classified documents.