Śatapatha Brāhmaṇa ("of a hundred paths") 2.5.2.14

2.5.2.14

atha pūrvedyuḥ | anvāhāryapacane 'tuṣāniva yavān kṛtvā tānīṣadivopatapya teṣāṃ karambhapātrāṇi kurvanti yāvanto gṛhyāḥ smustāvantyekenātiriktāni

And on the first day, after husking and slightly roasting barley on the Dakshinâgni, they prepare therewith as many dishes of karambha as there are members of the (sacrificer's) family, exceeded by one.