By will-power one can bring about a certain condition in one's body so that one's circulation takes a certain rhythm. It is decreased according to will. One can do the same in regulating one's pulsation by the power of will. No sooner has the will taken in hand the circulation and the pulsation of the body, than the will has in hand a meditation of hours. It is for this reason that sages can meditate for hours on end, because they have mastered their circulation; they can breathe at will, slower or quicker.