What is the geomantic saying that the millstone is buried underground?

In home geomantic omen, millstones and Yin Qi are very heavy objects. According to the query encyclopedia, in home feng shui, there are evil spirits of Qingshan or Duan Long, but they can only be placed after surveying the terrain and the status of Jiugong. A millstone is a machine used to process rice, wheat, beans and other grains into powder and pulp. It began to use human or animal power, and in the Jin Dynasty, the working people in China invented the waterwheel powered by water. The grinding disc is a two-layer plane with texture at the junction of the two layers. Particles enter the middle of the two layers from the upper hole, move outward along the grain, and are ground to form powder when rolling through the two layers.