William Walker Atkinson 
The Science of Breath (translated) [EPUB ebook] 

For thousands of years, yogis have believed that the breath is the essential link between body and mind, energizing a subtle body that connects the physical and mental aspects of our being. In this book, Swami Rama and two well-known American doctors explore the science of breath as the missing key to both physical health and the attainment of higher states of consciousness. Basic yogic breathing techniques are explained so that you can immediately begin working with the ancient science of breath.