Leonardo da Vinci sketched an odometer for measuring distance traveled.
His design connected a wheel to a counting mechanism. As the wheel turned, gears could register revolutions and release a fixed number of small objects into a container. Counting the objects would indicate how far the machine had moved, provided the wheel’s circumference was known.
This is a mechanical distance counter rather than a modern electronic vehicle instrument. Leonardo’s version belongs to a long history of measuring travel by relating wheel rotation to distance. Similar principles remain fundamental to mechanical mileage counters.
Leonardo did not invent the general idea of measuring journeys mechanically, and ancient devices such as the Roman hodometer had earlier precedents. His notebook design is notable for its detailed mechanical treatment and practical engineering purpose.