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The Doctrine and Practice of Yoga Including the Practices...

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(1) Inhale a complete breath very slowly, but steadily, through the nostrils, taking as much time as possible in the inhalation. (2) Retain for a few seconds. (3) Expel the air vigorously in one great breath, through the wide-opened mouth. (4) Rest the lungs by the cleansing breath. This would give you a good, rolling voice.

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The Doctrine and Practice of Yoga Including the Practices and Exercises of Concentration, both Objective and Subjective, and Active and Passive Mentation, an Elucidation of Maya, Guru Worship, and the Worship of the Terrible, also the Mystery of Will-Force, Project Gutenberg eBook #13300

NERVE VITALISING BREATH. THE RETAINED BREATH.