What are the lost technologies in ancient China?

There is an ancient China toy that looks like a bird. Its main body is made of glass. Its body is a glass tube, the upper end of the tube is a small ball, which is the head of a bird, and the lower end of the tube is a big ball, which is the tail of a bird. The ball is filled with liquid, and the lower end of the tube is submerged under the liquid surface. The whole bird is closed and stands on a seat similar to a bird's leg. It has a sharp mouth on its head and feathers on its tail. In order to hide the secrets of the bird, its body was painted black. And its magic is that if you put a glass of water in front of the bird, the bird will bend down, soak its mouth in the water, "drink" it, and then stand up. But when it stands upright for a while, it will bend down again, and when its beak is soaked in water, it will stand upright again. In this way, it keeps nodding and drinking water, just like a perpetual motion machine. But perpetual motion machine is impossible in scientific theory, so what is going on?

According to the interesting physics sequel edited by Belliman, a famous popular science writer in the former Soviet Union, someone once presented this painted "water-drinking bird" to Dr. Einstein and told him, didn't scientists say that perpetual motion is impossible? Now let you look at this perpetual motion machine. When Einstein saw and understood its principle, he was really amazed at the ingenious design of the "drinking bird". Therefore, this toy is called "a toy that Einstein was also surprised by".

Zhang Heng invented the world-famous drum car in his mind, and Ma Jun invented the direction indicator car in the Three Kingdoms period.

There are also Zhuge Liang's Trojan Horse, Hua Tuo's Five-Animal Play and the medical classic Qing Nang Shu. . .