Wilhelm Schickard (1592 – 1635) was a German polymath, professor of Hebrew and astronomy at the University of Tübingen and a friend of Johannes Kepler. In 1623, he designed the Calculating Clock, a machine intended to assist Kepler with his laborious astronomical calculations.
This device, which used a complicated system of gears and rotating cylinders, is now recognised as the first mechanical calculator in history. It’s omission from previous historical records was due to it being destroyed in a fire shortly after construction. Consequently, its very existence was largely forgotten until the 20th century.