Want to wear the first 23 digits of pi? Want to give other people a secret nerd handshake? Here’s the place to do it. A hat with a folded-over hem to keep your ears warm, with the first few digits of pi around the brim. The actual symbol pi is on top of the crown (perhaps a clue?)

Errata (11/07): slightly modified chart for the top (it’s been corrected in the pattern now too), because I always mess up decrease locations. Arrgh.