An hourglass or sandglass is an old device to measure time. Now, it is used more as a game timer or as ornament. Do you still remember the time when Windows OS use the icon of an hourglass as mouse cursor? It indicates that a task is still being processed.
“Hourglasses were the first dependable, reusable and reasonably accurate measure of time. The rate of flow of the sand is independent of the depth in the upper reservoir, and the instrument is not liable to freeze.
From the 15th century onwards, they were being used in a wide range of applications at sea, in the church, in industry and in cookery.
During the voyage of Ferdinand Magellan around the globe, his vessels kept 18 hourglasses per ship.” Source.
