When Marie Bosse was arrested in Paris, in January 1679, among her possessions was a copy of an unusual magical text. The Enchiridion Leonis Papae — Pope Leo's Handbook — has since acquired notoriety as a work of 'black magic', largely due to its association with the subsequent 'Affair of the Poisons', and the aura it acquired among 19th-century occult revivalists.