Śatapatha Brāhmaṇa ("of a hundred paths") 8.2.3

He then lays down the Prânabhrit (bricks). For at that time the gods said, 'Meditate ye!' whereby, doubtless, they meant to say, 'Seek ye a layer!' Whilst meditating, they saw even that layer, the wind: they put it into that (fire-altar), and in like manner does he (the priest) now put it therein.

He lays down the Prânabhrits,--wind, doubtless, is breath: it is wind (air) he thus bestows Upon him (Agni). On the range of the Retahsik (they are placed); for the Retahsik are these two (worlds): it is within these two (worlds) that he thus places the wind; whence there is wind within these two (worlds). He places them on every side: he thus places wind on all sides, whence the wind is everywhere. [He places them so as] on every side to run in the same direction: he thus makes the wind everywhere (to blow) in the same direction, whence, having become united, it blows from all quarters in the same direction. He lays them down alongside of the regional (bricks): he thereby places the wind in the regions, whence there is wind in all the regions.

And, again, as to why he lays down the Prânabhrits;--it is that he thereby bestows vital airs on these creatures. He places them so as not to be separated from the Vaisvadevîs: he thereby bestows vital airs not separated from the creatures. [He lays them down with, Vâg. S. XIV, 8], 'Preserve mine up-breathing! Preserve my down-breathing! Preserve my through-breathing! Make mine eye shine far and wide! Make mine ear resound!' He thereby bestows on them properly constituted vital airs.

He then lays down the Apasyâ (bricks). For the gods, at that time, spake, 'Meditate ye!' whereby, doubtless, they meant to say, 'Seek ye a layer!' Whilst meditating, they saw even that layer, rain: they put it into that (fire-altar) and in like manner does he now put it therein.

He put on the Apasyâs; for rain is water (ap); it is rain he thereby puts into it (the altar; or into him, Agni). On the range of the Retahsik (he places them), for, the Retahsik being these two (worlds), it is on these two (worlds) that he thereby bestows rain, whence it rains therein. He places them on every side: he thus puts rain everywhere, whence it rains everywhere. [He places them] so as everywhere to run in the same direction: he thereby bestows rain (falling) everywhere in the same direction, whence the rain falls everywhere, and from all quarters, in the same direction. He places them alongside of those referring to the wind: he thereby puts rain into the wind, whence rain follows to whatever quarter the wind goes.

And, again, as to why he lays down Apasyâs,--he thereby puts water into the vital airs. He places them so as not to be separated from the Prânabhrits: he thus places the water so as not to be separate from the vital airs. Moreover, water is food: he thus introduces food not separated from (the channels of) the vital airs. [He lays them down with, Vâg. S. XIV, 8], 'Make the waters swell! Quicken the plants! Bless thou the two-footed! Protect the four-footed! Draw thou rain from the sky!' He thereby puts water that is made fit, into those (vital airs).

He then lays down the Khandasyâ (bricks) for the gods, at that time, spake, 'Meditate ye!' whereby, doubtless, they meant to say, 'Seek ye a layer!' Whilst meditating, they saw even that layer, cattle (or beasts): they put it therein, and, in like manner, does he now put it therein.

He lays down the Khandasyâs; for the metres (khandas) are cattle: it is cattle he thus puts into it (or, bestows on him, Agni). On every side (he places them): he thereby places cattle (or beasts) everywhere, whence there are cattle everywhere. He places them alongside of the Apasyâs: he thus establishes the cattle on (or, near) water, whence cattle thrive when it rains.

And, again, as to why he lays down Khandasyâs. When Pragâpati was relaxed, the cattle, having become metres, went from him. Gâyatrî, having become a metre, overtook them by dint of her vigour; and as to how Gâyatrî overtook them, it is that this is the quickest (shortest) metre. And so Pragâpati, in the form of that (Gâyatrî), by dint of his vigour, overtook those cattle.

[He lays down four in front, with, Vâg. S. XIV, 9], 'The head is vigour,'--Pragâpati, doubtless, is the head: it is he that became vigour;--'Pragâpati the metre,'--Pragâpati indeed became a metre.

'The Kshatra is vigour,'--the Kshatra, doubtless, is Pragâpati, it is he that became vigour;--'the pleasure-giving metre,'--what is undefined that is pleasure-giving; and Pragâpati is undefined, and Pragâpati indeed became a metre.

'Support is vigour,'--the support, doubtless, is Pragâpati: it is he that became vigour;--'the over-lord the metre,'--the over-lord, doubtless, is Pragâpati, and Pragâpati indeed became a metre.

'The All-worker is vigour,'--the All-worker, doubtless, is Pragâpati: it is he that became vigour;--'the highest lord the metre,'--Pragâpati, the highest lord, doubtless, is the waters, for they (the waters of heaven) are in the highest place: Pragâpati, the highest lord, indeed became a metre.

These then are four kinds of vigour, and four metres; this (makes) eight,--the Gâyatrî consists of eight syllables: this, assuredly, is that same Gâyatrî in the form of which Pragâpati then, by his vigour, overtook those cattle; whence they say of worn-out cattle that they are overtaken by vigour (or, age), and hence (the word) 'vigour' recurs with all (these bricks). And those cattle which went away from him (Pragâpati) are these fifteen other (formulas): the cattle are a thunderbolt, and the thunderbolt is fifteenfold: whence he who possesses cattle, drives off the evildoer, for the thunderbolt drives off the evildoer for him. And in whatever direction, therefore, the possessor of cattle goes, that he finds torn up by the thunderbolt.