Śatapatha Brāhmaṇa ("of a hundred paths") 4.2.3.4

4.2.3.4

atha rājānamupāvaharati | tṛtīyaṃ vasatīvarīṇāmavanayati tatparva samaiti prathamamahottarasya savanasya karotyuttamam pūrvasya sa yaduttarasya savanasya tatpūrvaṃ karoti yatpūrvasya taduttamaṃ tadvyatiṣajati tasmādimāni parvāṇi vyatiṣaktānīdamitthamatihānamidamittham

Then he takes the king (Soma) down (from the cart), and pours one third of the Vasatîvarîs (into the Âdhavanîya trough). Thus the joint unites; for, indeed, he makes (the Ukthya cup) the first of the second pressing (Soma feast), and the last of the first: that which belongs to the second pressing he makes first, and that which belongs to the first he makes last. Thus he interlocks them; whence these joints are interlocked: this one overlapping thus, and this one thus.