As Jacob Loshin writes, magicians rely on a distinctive type of intellectual property– their tricks and the secrets of how to do them– that’s usually protected not by copyright or patent, but by informal but strongly enforced community norms.

Harry Blackstone‘s 1929 Secrets of Magic, written for lay audiences, doesn’t give away his profession’s signature effects, but explains more basic techniques and tricks. It does rely on a copyright, one that vanishes in 47 days. #PublicDomainDayCountdown