Excerpt from the Sūtra on the Samādhi of Sitting Meditation

Original text: 复次观身空界。常习此观。欲力精进力。一心力慧力。极为广大。便能举身。如大风力。致重达远。此亦如是。初当自试。离地一尺二尺。渐至一丈。还来本处。如鸟子学飞。小儿学行。思惟自审。知心力大。必能至远。学观四大。除却地大。但观三大。心念不散。便得自在。身无挂碍。如鸟飞行。当复学习。远作近想。是故近灭远出。

Explanation: Furthermore, one again contemplates the space element of the physical body, regarding the body as empty. By practicing and contemplating in this way constantly, the power of aspiration grows ever more vast, and the power of diligence, the power of one-pointed concentration, and the power of contemplative wisdom become extremely vast. At that time one can lift the body up, and the body gradually leaves the seat and rises into the sky. Just as a very powerful wind can blow a heavy object to a faraway place, so it is with lifting the body. At the beginning, one should test oneself little by little, letting the body leave the ground by one or two feet, gradually rising to ten feet, and then returning to the original place. It is like a fledgling bird learning to fly, or a small child learning to walk. One continually deliberates, examines, and evaluates one's own mental power, and at a certain point one knows that one's mental power has become very great, and that one can certainly fly to distant places.

Then one practices contemplating the four great elements of one's own body—earth, water, fire, and wind—removing the earth element from the mind and contemplating only the three great elements of water, fire, and wind, keeping the mind single-pointed and undistracted. Thereafter the body gains mastery and freedom, without any obstruction, like a bird in flight. At this time one should further learn and contemplate, taking the distant as near, extinguishing the notion of spatial distance, so that the body can instantly reach a distant place as if it were nearby.

Why is it that by taking the distant as near and extinguishing the notion of spatial distance, the body can instantly reach a distant place as if it were nearby? Because by contemplating in this way, the manas is made to believe it. Once the manas truly believes it and holds it as such, the tathāgatagarbha will necessarily follow the manas and transform and create such a realm. Supernatural powers work in this way, and all dharmas work this way: whatever the manas believes will appear. Changing the manas can change everything. Therefore, true self-confidence is the faith of the manas. As long as the manas believes, nothing cannot be accomplished—becoming a Buddha works on precisely this principle. Then, if the manas realizes no-self and believes in no-self, how great would the power of that no-self be? One eradicates the grasping on self and all afflictions, extinguishes all notions of self, the mind attains liberation, and one enters tranquil nirvāṇa.