The continuous change in the level of sand in an hourglass as time passes makes it an analog device. Perhaps the first analog computation was the use of graphs for the solution of surveying problems.

• 沙漏里随着时间的流逝而不断变动的沙线使之成为一种模拟搁置。也许第一次模拟计算是用图表解决普查问题。