All of us know the fact that the speech of some persons penetrates to the heart of the hearers while the speech of another will bring no effect on the mind, though he speaks beautifully. In the former, the speech is charged with prana, and in the latter, it is merely intellectual. The great profits and saints had the most wonderful control of prana, which gave them that sort of tremendous willpower that brought thousands toward them and made them think as the prophets. They could produce a tremendous amount of prana and their thought vibrations were charged with the pranic energy that gave them the power to sway the world. All willpower comes from the control of prana.
THE COMPLETE ILLUSTRATED BOOK OF YOGA, Swami Vishnu-devananda, 225, !960, 1988, The Julian Press, Inc.