Jefferson Wheel Cipher
Invented by Thomas Jefferson around 1795, independently reinvented by Etienne Bazeries
in 1891 as the "Cylindrical Cryptograph." The US Army adopted it as the M-94 in 1922.
26 wooden discs, each with a scrambled alphabet around its rim, are threaded onto an axle.
The sender rotates each disc to spell the plaintext on one row, then reads
the ciphertext from any other row. The recipient, having identical discs in the same order,
sets the ciphertext and searches for a readable plaintext row. Remained in US military
service until 1942.