Leonardo da Vinci designed an odometer to measure the distance traveled by a cart.
His cart-based device used a wheel that turned as the vehicle moved. A system of gears transferred the wheel’s rotation to a display mechanism, allowing the device to record distance. In one commonly described arrangement, the mechanism released a pebble at regular intervals into a container, providing a count of traveled units.
An odometer measures distance, while a speedometer measures speed. Leonardo’s design was therefore not a speed-measuring instrument, even though both devices are associated with vehicles today.
Leonardo was interested in accurate surveying and military engineering, fields in which measured distances were important. The design is part of a long history of mechanical distance counters, eventually leading to the odometers used in automobiles and other vehicles.