Yogi Ramacharaka 
Science of Breath [PDF ebook] 
A Complete Manual of the Oriental Breathing Philosophy of Physical, Mental, Psychic and Spiritual Development

The Science of Breath points out the way to physical health along the lines of what Western scientists have termed "deep breathing, " etc., but also goes into the less known phases of the subject, and shows how the Hindu Yogi controls his body, increasing his mental capacity, and develops the spiritual side of his nature by the "Science of Breath." By rhythmical breathing one may bring himself into harmonious vibration with nature, and aid in the unfoldment of his latent powers. He knows that by controlled breathing he may not only cure disease in himself and others, but also practically do away with fear and worry and the baser emotions.