The System of the Vedanta according to Badarayana's Brahma-Sutras and Cankara's Commentary c8.s7.t2.5.3

c8.s7.t2.5.3

So too the pericardium is in close relationship (anuguṇa p. 793, 4) with the place of deep sleep. For the envelope of the heart is termed pericardium, purītat; what is in the heart is also in the purītat, just as what is in a town is surrounded by the walls of the town (p. 793, 8). Of the three places of deep sleep, veins, pericardium and Brahman, the two first are therefore only to be regarded as entrances (p. 793, 13). "The “veins too, or the Puritat are only the receptacle of the Upâdhis “of the soul; in them its organs sojourn [probably only the “Indriyas, and if a removal from its natural position be “assumed, the Manas]. For apart from the connection with “the Upâdhis, the soul in itself (svatas) needs no receptacle “but in its non-difference from Brahman reposes in its own “majesty” (Chând. 7, 24, 1), and thus identity (tâdâtmyam), not a relation of receptacle and contents, exists, between it and Brahman (p. 794, 2); “true the entrance of the soul into Brahman is never unrealised; it cannot give up its own nature; “but in dream and waking by virtue of its mingling with the “Upâdhis it is as though the soul had passed into a different “nature; therefore the release from the Upâdhis in deep sleep “is regarded as an entrance of the soul into its own nature” (p. 794, 7). The aim of deep sleep, the suspension of individual cognition, would not be attained by a mere entrance into veins and Puritat, for (p. 794, 14) they involve plurality (bheda-vishaya);