Skanda Purana 7.18.89_253

7.18.89_253

tatsaṃhṛtya munirbhūyo vyāpi bhūtaṃ pravistṛtam .
nāḍīvāyupracāreṇa bhūyobhūyastathārabhet37 . .43 . .
sa pūrvāpararātre tu sātvikaṃ38 ceta39 ucyate .
madhyāhne cāparāhṇe ca kṛṣṇaṃ40 dhyāyīta tāmasam . .44..

Having withdrawn that, the sage should again and again undertake [this] / with the circulation of breath through the subtle channels, all-pervading and fully expanded. (43) / In the early and late parts of the night, the mind is said to be sattvic; / at midday and in the afternoon, one should meditate on the dark, tamasic [state]. (44)