Leonardo da Vinci designed an escapement mechanism using a pendulum-like regulator for a clock.
His notebooks include studies of clockwork, including gears, weights, and mechanisms intended to control the release of energy. An escapement allows a clock's gear train to advance in measured steps instead of unwinding freely. Leonardo's proposed regulator used oscillating motion to help maintain a more regular rate.
The design should not be called the first pendulum clock. Galileo Galilei studied pendulum timekeeping in the 17th century, and Christiaan Huygens built the first practical pendulum clock in 1656. Leonardo's earlier sketch was exploratory and did not produce a working precision clock.
The distinction matters because a clock's oscillator and escapement perform different jobs. The regulator establishes a rhythm, while the escapement converts that rhythm into controlled gear movement. Leonardo's drawings show a sophisticated understanding of both functions.