Om: this syllable, this imperishable, is the All. Its expansion is what has been, what is, what shall be. All, verily, is Om. And whatsoever else surpasses the three times, this also is Om. For all this is the Eternal, this is the Divine Self; and this Divine Self has four measures.
Standing in waking, outwardly perceiving, of sevenfold form, with nineteen energies, experiencing the gross, Common-to-all-men, this is the first measure.
Standing in dream, inwardly perceiving, of sevenfold form, with nineteen energies, experiencing the subtle, the Radiant, this is the second measure.
Where entering into rest, he desires no desire, nor beholds any dream, this is dreamlessness. Standing in dreamlessness, unified, a sphere of spiritual perception, formed of joy, experiencing joy, whose energy is spiritual consciousness, the Wise Seer is the third measure. He is Lord of all, he is all-knowing, he is the inner ruler, he is the source of all, the forth-going and the indrawing of lives.
Nor outwardly perceiving, nor inwardly perceiving, nor perceiving in both ways, nor a sphere of spiritual perception, nor perception, nor non-perception; invisible, inapprehensible, ungraspable, indistinguishable, unimaginable, unindicable, whose essence is realization of oneness with the Eternal, where forth-going is ended, still, benign, beyond duality, is held to be the fourth; this is the Divine Self, this is the goal of wisdom.
Mandukya Upanishad Translation Charles Johnston