Contrary to popular belief, hatha yoga exercises are not designed to make fat people thin or to make the body immortal, but to help unblock the gross and subtle nervous systems so that the “life air” can flow freely through the body (specifically, from the base of the spine to the top of the head).
Just as there is no perfectly simple way to explain a complex principle of physics or biochemistry to a layman, so there is no perfectly simple way to explain the subtle material technology known to the yogis.
As a yogi, you see the body that covers you—the pure atma or self—as being made of layers of material energy, from the subtle to the gross.
Jagad Guru Chris Butler, Science of Identity Foundation
For thousands of years, sages have taught various methods of physical exercises and meditations that are conducive to bringing about an out-of-body experience.
The fact is that you know you existed five years ago, and you know you exist today. Although you still exist, you know that the body you had five years ago does not exist today. Therefore, you know that your existence is not dependent on the existence of any one body you may have on at any particular moment—whether it is a “baby” body, an “adolescent” body, an “old” body, or whatever.
Jagad Guru Chris Butler, Science of Identity Foundation