A timekeeper is an hourglass (also known as a sandglass, sand timer, sand clock, or egg timer). It consists of two glass bulbs connected vertically by a small neck that allows a regulated flow of a material (in this example, sand) from the top to the lower bulb. The top and bottom bulbs are generally symmetrical, so the hourglass measures the same length no matter which way it is turned. The length of time a particular hourglass measure is influenced by the quantity and coarseness of the particulate matter, as well as the bulb size and neck width.

An hourglass has been shown as a symbol of the passage of time in art since antiquity, notably on tombstones and other monuments. In a literal sense, the form of a winged hourglass has been used to symbolize the well-known expression “time flies.”

A Frankish monk called Liutprand, who served at the cathedral in Chartres, France, constructed the earliest known instance of the hourglass in the 8th century CE. The hourglass was not generally known until the 14th century, with the first certain evidence being in Ambrogio Lorenzetti’s fresco Allegory of Good Government from 1338.

Marine sandglass has been used since the fourteenth century. The majority of the written records came from logbooks kept by European ships. During the same time period, it occurs in a number of papers and ship shop listings. The first documented reference to a maritime sandglass dates from around 1345, in a receipt of Thomas de Stetesham, clerk of the King’s ship La George; translated from the Latin, the ticket reads: around 1345:

Onboard ships, marine sandglasses were quite popular since they gave the most accurate timekeeping when at sea. The hourglass, unlike the clepsydra, was unaffected by the ship’s motion while sailing. The hourglass used granular materials instead of liquids since the clepsydra was prone to condensation inside it during temperature changes, providing it more exact readings. The hourglass proved to be a reliable instrument for calculating longitude, or the distance east or west from a particular location.

The hourglass was equally popular on land. As the usage of mechanical clocks to display the timings of events such as church services became more popular, the demand for time-measuring devices grew, resulting in a “need to keep track of time.” Hourglasses were reasonably inexpensive to make since they required no particular technology and their contents were widely available, and their uses grew more practical as their manufacturing spread.

In churches, families, and businesses, hourglasses were commonly used to measure sermons, cooking time, and time spent on breaks from labor. As they were used for increasingly frequent tasks, the hourglass form began to fade away. Because they allowed for more delicate timing, smaller versions were more practical and popular.

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