Perhaps the most underrated invention in history is the humble hourglass. Invented in Europe during the late 13th or early 14th century, the sand glass complemented a nearly simultaneous invention, the mechanical clock. The mechanical clock with its bell was a centralized way of broadcasting the hours day and night; the sand glass was a portable way of measuring shorter periods of time. These clocks were made using very different and independent techniques, but their complementarity fun...
