The Leonardo da Vinci machine that recorded distance by dropping stones into a box as a cart moved was an odometer.
Leonardo’s odometer design adapted the idea of measuring travel through wheel rotation. As the cart moved, a wheel turned a sequence of gears. The gearing was arranged so that a particular amount of wheel movement triggered the release of one stone into a container. Counting the stones gave an estimate of the distance traveled.
This was not the first odometer in history. Ancient Greek and Roman engineers had already developed distance-measuring devices, including instruments associated with Vitruvius and Heron of Alexandria. Leonardo’s contribution was a detailed Renaissance design that made the mechanism visually clear and practical for surveying or road measurement.
The device is sometimes confused with Leonardo’s military carts or lifting machines. Its purpose was measurement: it converted continuous wheel motion into countable units rather than transporting people or attacking an enemy.