Chaucer wrote the following cryptogram into his work The Equatorie of the Planetis:

According to cryptologist David Kahn, the cryptogram reads, in part, "This table servith to entre in to the table of equacion of the mone on either side." Granted, that's a pretty damn boring message, but what the hell--you can use this piece of arcana to impress the pseuds next time you're trapped at a cocktail party.