What early calculating device is Leonardo da Vinci often credited with sketching?

Leonardo da Vinci is often credited with sketching a mechanical calculator.

A drawing in the Codex Madrid contains a system of gears that has been interpreted as a device for performing arithmetic. The mechanism is usually described as a calculator concept rather than a confirmed completed machine. Its toothed wheels could, in principle, transmit numerical changes from one place to another, a basic requirement for mechanical calculation.

The drawing was rediscovered in the twentieth century, long after Leonardo’s death. Because the surviving sketch is incomplete and its purpose is debated, historians avoid treating it as proof that Leonardo built a working calculator. Reconstructions have explored how the gears might have operated, but they cannot establish what Leonardo actually completed.

Leonardo was not the first person to imagine mechanical calculation. Ancient devices and later calculating instruments had different origins, and the first widely recognized mechanical calculator was Blaise Pascal’s Pascaline, developed in the seventeenth century. Leonardo’s importance here is as an early documented designer of a geared arithmetic mechanism.