Introduction to the clepsydra: The clepsydra model is a set of ancient timing tools, consisting of several water containers arranged in the form of a ladder. There are holes on the underside of each container, and water drips and leaks into the next container in turn. The bottom container has no holes, and is equipped with an "arrow" engraved with a time scale. As the water surface of the drip rises, the "arrow" slowly floats, and the time can be read from the exposed scale. Shen Kuo reformed the clepsydra, changing the curved copper leakage tube into a straight-necked jade mouth, and moved its position to the lower part of the kettle body. This way the water flows more smoothly and the spout is much stronger and more durable.