Leonardo da Vinci designed a hygrometer to record changes in humidity.
A hygrometer measures the moisture content of air. Leonardo’s proposed instrument used materials whose weight or behavior changed with moisture, allowing an observer to compare damp and dry conditions. The design reflects his habit of treating natural phenomena as measurable mechanical effects.
Leonardo’s hygrometer was an early conceptual instrument rather than a modern electronic sensor. Historical accounts connect the design with a balance arrangement involving absorbent material and a reference weight. The device offered a way to detect atmospheric moisture, an important subject for someone studying weather, evaporation, air, and water.
The instrument should not be confused with an anemometer, which measures wind speed, or a barometer, which measures atmospheric pressure. Later hygrometers used hair, chemical substances, or electrical sensors, but Leonardo’s proposal belongs to the early history of humidity measurement and scientific instrumentation.