Breath Power… Keep it Fresh
"Kokyu-Ho (the way of Kokyo) or 'breath power techniques,' constitute the fourth pillar of Aikido. Morihei (the founder of Aikido) said 'Breath is the thread that ties creation together. When the myriad variations of breath in the universe can be sensed, the individual techniques of Aikido are born.' In the old days, Kokyu-Ho techniques, thought to contain the secret of true power, were never taught publicly."
-From "The Essence of Aikido", by John Stevens, Kodansha International Ltd., 1993, pp. 151