In the late 1870s, a magician named Buatier De Kolta was mesmerising audiences in Paris by producing big bunches of paper flowers from an empty roll of paper. Nobody knew how the trick was achieved, until a gust of wind blew one of the flowers on to the floor in front of the stage. A magician in the audience seized it and ran out – De Kolta’s trick was soon being performed by many of his rivals.

The story is told by Jacob Loshin, a recent graduate from Yale Law School, in a working paper on how magicians protect their tricks. Such outright thefts would be hard to imagine today because magicians have developed a professional code of conduct to defend their most valuable property: their ideas.