OM! - This Imperishable Word is the whole of this visible universe. Its explanation is as follows: What has become, what is becoming, what will become, - verily, all of this is OM. And what is beyond these three states of the world of time, - that too, verily, is OM.
All this, verily, is Brahman. The Self is Brahman. This Self has four quarters.
The first quarter is Vaisvanara. Its field is the waking state. Its consciousness is outward-turned. It is seven-limbed and nineteen-mouthed. It enjoys gross objects.
The second quarter is Taijasa. Its field is the dream state. Its consciousness is inward-turned. It is seven-limbed and nineteen-mouthed. It enjoys subtle objects.
The third quarter is Prajna, where one asleep neither desires anything nor beholds any dream: that is deep sleep. In this field of dreamless sleep, one becomes undivided, an undifferentiated mass of consciousness, consisting of bliss and feeding on bliss. His mouth is consciousness.
This is the Lord of All; the Omniscient; the Indwelling Controller; the Source of All. This is the beginning and end of all beings.
That is known as the fourth quarter: neither inward-turned nor outwardturned consciousness, nor the two together; not an indifferentiated mass of consciousness; neither knowing, nor unknowing; invisible, ineffable, intangible, devoid of characteristics, inconceivable, indefinable, its sole essence being the consciousness of its own Self; the coming to rest of all relative existence; utterly quiet; peaceful; blissful: without a second: this is the Atman, the Self; this is to be realised.
This identical Atman, or Self, in the realm of sound is the syllable OM, the above described four quarters of the Self being identical with the components of the syllable, and the components of the syllable being identical with the four quarters of the Self. The components of the Syllable are A, U, M.