pen. By switching the number and order of its internal wheels, different letters, and hence different messages, could be produced. In effect, it could be mechanically "programmed" to read instructions. Along with two other complex machines, the doll is at the Musée d'Art et d'Histoire of Neuchâtel, Switzerland, and still operates.

In 1831-1835, mathematician and engineer Giovanni Plana devised a Perpetual Calendar machine,