Pranayama

The Science of Pranayama is a free online book from the Divine Life Society. Sri Aurobindo did some pranayama in the early years of his sadhana. Here are some things he had to say about it;
"What I did was four or five hours a day pranayama..."
"I said clearly that the pranayama brought me nothing of any kind of spiritual realisation".
"After four years of pranayama and other practices on my own, with no other result than an increased health and outflow of energy, some psycho-physical phenomena, a great outflow of poetic creation, a limited power of subtle sight(luminous patterns and figures,etc.)mostly with the waking eye..."
"The results were remarkable. I used to see many visions, sights and figures. I felt an electric power around my head. My powers of writing were nearly dried up - they revived with a great vigor. I could write prose and poetry with flow. That flow has never ceased since then. If I have not written afterwards it is because I had something else to do. But the moment I want to write it is there. Thirdly, great health. I grew stout and strong, the skin became smooth and fair and there was a flow of sweetness in the saliva. I used to feel a certain aura around the head. There were plenty of mosquitoes but these did not come to me."