During the period of practice, breathe as slowly as possible without feeling discomfort. This is done in order to come nearer to the possibility of holding the breath altogether, for in the arrest of its movement an arrest of the movement of thoughts automatically follows. The slowness is achieved by prolonging the time given to inhaling as well as the time given to exhaling. This must be done by degrees, gently not forcibly. It is really an attempt to imitate the slower breath rhythm observable in a sleeping man, for the layers of consciousness through which the meditator must pass are comparable to those which accompany the dreaming and dreamless states. Holding the breath means holding the inhaled breath--a physiological condition in which there are certain dangers to the lungs, the blood-vessels, and the brain. Consequently, a grave warning must always go out to those who risk health and sanity by carrying breathing exercises to this extreme extent.
-- Notebooks Category 4: Elementary Meditation > Chapter 2 : Place and Condition > # 246
