The term “Renaissance Man” refers to a person who has excelled at several disciplines completely different from one another: painting, say, and mechanical engineering. That was what Leonardo da Vinci, who actually lived during the Renaissance period, accomplished. Best known today for his paintings of The Last Supper and the Mona Lisa, he was also a prolific inventor, creating hundreds of sketches of machines that couldn’t be built for centuries. He could even be said to have invented the world’s first calculator.

On this day, February 13, in 1967, American researchers working in the National Library of Spain in Madrid happened upon two previously unknown sketches of da Vinci. Curious to see what value the two discoveries had, they enlisted the help of IBM to build the complicated device on the plans. What came back amazed everybody.

The device had thirteen interlocking wheels, each with ten faces numbered sequentially from 0 to 9. After the first wheel reached 9, the second wheel would engage, and so on. It was the world’s first adding macine — or a sketch of one anyway. No machines with that many moving parts could have operated in da Vinci’s time due to friction. But for a man who invented the helicopter, practicality was not an obstacle.