Leonardo da Vinci designed a water clock to track the passage of time.
Leonardo studied water clocks as part of his broader interest in hydraulics and precise measurement. In a water clock, water flows into or out of a container, and the changing water level indicates elapsed time. Leonardo’s designs explored controlled flow and mechanical motion rather than relying only on the position of the Sun.
Water clocks were much older than Leonardo. Ancient civilizations used them, and Greek and Roman engineers developed increasingly elaborate versions. Leonardo’s contribution was to examine how water movement could be connected to mechanisms and regulated more consistently.
A water clock is not the same as a sundial, which uses the Sun’s apparent motion, or an hourglass, which uses falling sand. Leonardo’s notebooks contain many proposals that were never fully constructed, so his water-clock studies should not be treated as proof that he built a complete, commercially used clock.