Scottish mathematician John Napier may have been known for his contributions toward logarithms, but was also the inventor of a tool called Napier’s Bones (also called Napier’s Rods). These were multiplication tables inscribed on strips of animal bone or wood. Wilhelm Schickardt would eventually build the first calculating machine based on Napier’s Bones, a device that could add, subtract, and—with help— multiply or divide.

Napier was also the “instigator” in another discovery: In 1621, English mathematician and clergyman William Oughtred (1575–1660) used Napier’s logarithms as the basis for the slide rule (a ruler-like instrument used long before hand-held calculators came in vogue). Oughtred not only invented the standard rectilinear slide rule, but also the circular slide rule, which was an extremely useful tool that remained in common usage for more than three hundred years. (For more about Oughtred, see “Math Basics.”)