Leonardo da Vinci devised an early hygrometer to indicate changes in atmospheric humidity.
The instrument used a balance arrangement with materials that responded differently to moisture, including absorbent substances and materials less affected by dampness. As humidity changed, the balance would shift. This made invisible water vapor indirectly measurable through a visible mechanical movement.
A hygrometer measures humidity, not wind speed or air pressure. Leonardo’s design belongs to the early history of meteorological instruments, when scientists were developing ways to quantify properties of air that could not be seen directly. It was not a modern electronic humidity sensor and did not provide the precise digital readings familiar today, but it represented an important step toward systematic atmospheric measurement.