Śatapatha Brāhmaṇa ("of a hundred paths") 4.4.3.4

4.4.3.4

droṇakalaśe gṛhṇāti | vṛtro vai soma āsīttaṃ yatra devā aghnaṃstasya mūrdhodvavarta sa droṇakalaśo 'bhavattasminyāvānvā yāvānvā rasaḥ samasravadatirikto vai sa āsīdatirikta eṣa grahastadatirikta evaitadatiriktaṃ dadhāti tasmāddroṇakalaśe gṛhṇāti

He draws it in the Dronakalasa. Now Soma was Vritra. When the gods slew him, his head rolled off: it became the Dronakalasa. Thereinto flowed together so much of the juice as it could hold; that was in excess; and so is this graha in excess: he thus puts the excess. to the excess,--therefore he draws it in the Dronakalasa.