The System of the Vedanta according to Badarayana's Brahma-Sutras and Cankara's Commentary c8.s7.t3.2

c8.s7.t3.2

Besides the states of waking, dreaming, deep sleep, and death there is a special state, which is different from all, an intermediate condition between several of them, namely swooning (p. 799, 12). It is in the first place not the waking state; for in it the senses no longer perceive the objects. True the arrow maker perceives nothing beyond his work when he is buried in it; but he has all the same consciousness and control over his body, both of which are absent in the fainting person (p. 800, 7. 11). Further swooning is not dream-sleep on account of the accompanying unconsciousness, and not death because it is distinguished from it by bodily warmth and breath. That is why people look for warmth in the region of the heart, and breath in the nostrils to find out whether anyone is dead or only fainting; if both are absent people say he is dead and fetch wood to burn the body; if on the other hand warmth and breath are still present, he is cared for in order to restore him to consciousness (p. 800, 13). By his coming to himself again we see that he was not dead: for from Yama’s realm no return is possible [though Naciketas in the Kâthaka-Upanishad, like Er, the Armenian, in Plato Rep. 10, 13 p. 614 B, gains information as to the Beyond by sojourning in the kingdom of the dead]. Finally swooning is not deep sleep either; for while fainting is characterised by interrupted breathing, trembling of the body, a frightful expression on his face, and widely opened eyes, a person in deep sleep has a peaceful expression; he draws his breath regularly, and has his eyes closed, and his body does not tremble; moreover he is waked by merely stroking him with the hand, while not even blows with a hammer can rouse a fainting person. [Perhaps from observations during torture]. The causes of the two phenomena are different also; in the one case the blows of a club and the like produce it, in the other simple weariness (p. 801, 10). Therefore swooning is half deep sleep, not in the sense that it is a half union with Brahman, but in so far as it is intermediate between deep sleep and death. It is a gate of death (p. 802, 9): "if there remain works [that still have to be atoned "for] speech and consciousness return; if nothing remains "breath and warmth depart."