On the show today, the story of an innovation that changed the way the world works, and of the man who made this innovation possible. Luca Pacioli was a monk, a mathematician, a magician and possibly, the boyfriend of Leonardo da Vinci. Jane Gleeson-White, author of Double Entry: How the Merchants of Venice Created Modern Finance, tells us the story of Pacioli and how his book on mathematics changed business across the planet. Note: This episode was originally posted last year. Download the Planet Money iPhone App. Music: Noah & The Whale’s “Tonight’s the Kind of Night.” Find us: Twitter/ Facebook/ Spotify/ Tumblr