Leonardo da Vinci designed a water clock that used water movement and a float to indicate elapsed time.
In a water clock, water flows at a controlled rate into or out of a vessel. The changing water level moves a float, and that motion can be transferred to a pointer or scale. Leonardo’s designs explored ways to make the flow and indication more regular, addressing a central problem in early timekeeping.
A water clock does not depend on sunlight like a sundial or falling sand like an hourglass. It also predates the widespread use of accurate pendulum clocks. Leonardo’s concept developed an ancient timekeeping principle with more elaborate mechanical control.