Pascal's Calculating Machine

A brass Pascaline, one of the mechanical calculators Blaise Pascal began designing in 1642, while his father was working as a tax official in Rouen. Each spoked wheel along the front enters one digit, and the windows above show the running total; inside, a carry mechanism passes a one to the next column when a wheel goes past nine. The Musée des Arts et Métiers in Paris holds several surviving examples, including this one.