Śatapatha Brāhmaṇa ("of a hundred paths") 5.1.2.15

5.1.2.15

atha pūrvedyuḥ | dvau kharau kurvanti puro 'kṣamevānyam paścādakṣamanyaṃ netsomagrahāṃśca surāgrahāṃśca saha sādayāmeti tasmātpūrvedyurdvau kharau kurvanti puro 'kṣamevānyam paścādakṣamanyam

And on the preceding day they prepare two earth-mounds, the one in front of the axle, and the other behind the axle: 'Lest we should deposit together the cups of Soma, and the cups of Surâ,'--this is why, on the preceding day, they prepare two mounds, one in front, and the other behind the axle.