The meaning of the word yoga is unity or connection, and mantrayoga means the sacred union between the outer life and the deeper life. For the Yogis found out that there are psychological indications: one of the tendencies of the breath is to go outward, the other inclination is to go inward. These two tendencies are to be found in nature also: in the ebb and the flow, in the sunset and sunrise. One sees this difference in oneself: the vibrations of one's own body and action are very different in the morning and in "the evening. The Yogis therefore regulated the rhythm of the circulation, of the heart and of every action of the breath, with the help of vibration, of music, of both tone and rhythm. This brought them from the audible vibrations to the inward vibrations, which means: from sound to breath, which in the language of the Hindus are one and the same. It is sura which is a name for sound and for breath. The one blends into the other, because it is the same thing in the end. It is the breath of an object which may be called a sound, and it is the audibility of the breath which may be called voice. Therefore breath and voice are not two things. Even breath and sound are not two things, if one can understand that both have the same basis.