This egg timer is a form of hourglass which measure the time in minutes. In this case from left to right, five minutes, four minutes and three minutes. Factors which affect the time measured include the amount of crystals, the bulb size, the neck width and the sand quality. The hourglass must be tightly sealed to exclude moisture. The hourglass is thought to have originated in Ancient Greece. It was widely used by the 1300s.The hourglass is often used as a visual symbol representing tim