Leonardo da Vinci’s invention for measuring distances traveled by a cart with a drum-and-rope system was an odometer.
His design used a cart wheel to drive a series of gears. After a set number of wheel rotations, the mechanism released a small weight into a container. Counting the collected weights indicated how far the cart had traveled. This was a mechanical way to convert wheel movement into a distance measurement.
The design appears among Leonardo’s engineering studies from the late fifteenth century. It was not a modern electronic instrument, but it expressed the same basic principle used by later mechanical odometers: a known wheel circumference combined with counted rotations.
A common mix-up is calling the device a speedometer. An odometer measures distance, whereas a speedometer measures speed. Leonardo also designed surveying and military machines, but the drum-and-rope distance recorder is specifically associated with an odometer concept.