Historical Evidence of Hourglasses

hourglass on strings

The Guinness Book of Records says the first solid proof of hourglasses were in 14th century ship inventories where devices in which sand fell from one glass globe into another. These are far more accurate on the seas than the earlier clocks made of water since the movement of the seas would make the clock-water move as well.

Earlier time pieces were made using water. These had problems due to atmospheric pressures which made the water flow faster or slower depending on air temperatures and moon cycles.