Śatapatha Brāhmaṇa ("of a hundred paths") 7.2.2.18

7.2.2.18

yadvevainaṃ vikṛṣati | etadvā asmindevāḥ saṃskariṣyantaḥ purastātprāṇānadadhustathaivāsminnayametatsaṃskariṣyanpurastātprāṇāndadhāti lekhā bhavanti lekhāsu hīme prāṇāḥ

And, again, why he ploughs through him,--the gods being about to put him (Pragâpati) together, thereby in the first place put the vital airs into him; and in like manner does this (Sacrificer), being about to put him together, thereby in the first place put the vital airs into him. They (the furrows) are lines, for these vital airs (move) in lines (channels).