The hourglass, also known as a sand timer or sand clock, has been a significant instrument for measuring time since its inception, believed to be around the 8th century AD. Unlike earlier water clocks, or clepsydras, which were affected by temperature, the hourglass provided a more consistent measure of time due to its use of sand.

Historically, the hourglass has held a symbolic place in the portrayal of the concept of time in art, literature, and iconography, often representing the inexorable march of time and the finite nature of human life. In a more practical sense, its accuracy and reliability made it an essential tool for various applications, most notably in navigation. Before the advent of mechanical timepieces, seafarers relied on the hourglass to measure time intervals at sea, which, when used in conjunction with other tools like the astrolabe, allowed for basic dead reckoning in navigation.

The hourglass had to be of precise construction to ensure accuracy, with exact amounts of finely graded sand that would run from one bulb to another in a set time. However, it was not without limitations; the need to manually invert the hourglass to continue time measurement made it less practical for longer durations. Despite its eventual obsolescence with the rise of more precise mechanical clocks, the hourglass remains a powerful emblem of the passage of time, enduring in its elegance and simplicity.