Edgar Allen Poe had a long fascination with cryptology. Ciphers played a large roll in The Gold Bug and many of his works referred to "secret writings." He also ran his own cryptography contest where he challenged his readers to send him ciphers and he would break them and publish the solution. He claimed to have solved all legitimate ciphers sent to him except two sent in by a Mr W. B. Tyler, a person who may have never existed but actually been a pen name for Poe.
These two ciphers sat unsolved for 150 years.