Śatapatha Brāhmaṇa ("of a hundred paths") 3.5.4.7

3.5.4.7

atho itarathāhuḥ | aparayorevāgra uttaram parilikhedatha pūrvayordakṣiṇamathāparayordakṣiṇamatha pūrvayoruttaramityatho api samīca eva parilikhedetaṃ tvevottamam parilikhedya eṣa pūrvayoruttaro bhavati

But they say conversely, that he should mark off first the left one of the two behind; then the right one of those in front; then the right one of those behind; and then the left one of those in front. Or he may also mark them off in one and the same direction: but let him, in any case, mark off last of all the one which is on the left of those in front.