B.K.S. Iyengar demonstrates Ujjayi breathing
The mind is the master of the senses, and the breath is the master of the mind. And if the nerves, which are thousands of kilometers apart in the nervous system, vibrate rhythmically, then this rhythmic vibration of the nerves becomes the master of the breath. I will show you the inhalation and exhalation to experience the rhythm of the sound of the breath...
— B.K.S. Iyengar