Śatapatha Brāhmaṇa ("of a hundred paths") 11.7.4

Now, when he who is about to perform an animal sacrifice makes a stake one cubit long, he thereby gains this (terrestrial) world; and when (he makes) one two cubits long, he thereby gains the air-world; and when be makes one three cubits long, he thereby gains the heavens; and when he makes one four cubits long, he thereby gains the regions. But, indeed, that sacrificial stake of the (ordinary) animal sacrifice is either three or four cubits long, and one that is above that belongs to the Soma-sacrifice.

As to this they say, 'Should he offer the butter-portions or not?'--'Let him offer them,' they say; 'for the two butter-portions are the eyes of the sacrifice, and what were man without eyes?' For as long as a co-sharer is not bought off by (receiving) a share of his own, so long does he consider himself not bought off; but when he is bought off by a share of his own, then, indeed, he considers himself bought off: when the Hotri, on that occasion, recites, 'Endow the Rakshas with blood!' he buys him off by (assigning to him) a share of his own.

For on that occasion the anguish of the victim, in being slaughtered, becomes concentrated in the heart, and from the heart (it flows) into the spit. Thus, if they (were to) cook the animal together with the heart, the anguish would again spread all over the animal: let him therefore cook it (the heart) after spitting it from the side on a stick.

He makes an underlayer of ghee (in the offering-ladle): this he makes a type of the earth; he then puts a chip of gold thereon: this he makes a type of fire; he then puts the omentum thereon: this he makes a type of the air; he then puts a chip of gold thereon: this he makes a type of the sun; and what (ghee) he pours upon it, that he makes a type of the heavens. This, then, is that five-portioned omentum,--fivefold is the sacrifice, fivefold the sacrificial animal, and five seasons there are in the year: this is why the omentum consists of five portions.