pranayama
pranayama, in the Yoga darshan (system) of Indian philosophy, the fourth of eight stages intended to lead the aspirant to samadhi, a state of perfect concentration. The immediate goal of pranayama is to reduce breathing to an effortless even rhythm, thus helping to free the individual’s mind from attention to bodily functions.
Yoga, like most Hindu philosophies, recognizes four states of consciousness—waking, sleep with dreams, sleep without dreams, and a state resembling cataleptic consciousness—each of which has its own respiratory rhythm. By prolonging each respiration as long as possible in simulation of the unconscious states during which respiration is slower than in the normal waking state, the yogi ultimately learns to pass from one state to another without loss of consciousness.