William Walker Atkinson 
Hindu-Yogi Science of Breath 

This little book contains 34 meaningfully distinct exercises ranging from basic breathing to psychic healing. One core takeaway is that there is one common core breathing technique: rhythmic complete breathing. This is an informative styled book and it’s very well written for its kind. The science part is simplified for everyone to understand and the suggested breathing techniques are easy to implement into my daily life. (Goodreads)