What is meant by "Internal inspection" (内视)?

Internal inspection refers to closing your eyes and looking at a certain part of your body without external interference and distracting thoughts, also known as "internal inspection".

Its purpose is to be quiet. 

"The Secret Text of Tsinghua University" says: "Those who can't be calm in mind can't simply call their hearts, cover their minds and serve their gods, and the two serve each other. If you want to be quiet, you must first control your eyes. Those who are wandering in the house will wander in the eyes and serve your heart, so you can suppress your eyes and make them return to your heart. " Therefore, when you look at the inside with your eyes, your mind is concentrated, your vitality is abundant, you look back and look inside, and your mind is calm and calm. When practicing, concentrate on rest, put your tongue on the palate, pay attention to your mind and look down at the abdomen, and you will soon be quiet.