Wilhelm Schickard

Wilhelm Schickard taught Hebrew and astronomy in Germany until his death in 1635, but his real mark surfaced only in the 1950s when a Kepler biographer found two lost letters from 1623 and 1624 describing a calculating clock. The drawings had actually been published repeatedly since 1718, though no one connected them to the calculator story. Schickard's design paired an adding machine with a rotated Napier's bones system for multiplication - the first known hybrid of its kind - but the single-tooth carry mechanism didn't work reliably and the prototype was never finished. Later 17th-century inventors followed his path, combining rods and adding wheels, though scholars argue his incomplete work had no direct influence on what came after. He's been called the father of the computer age anyway.