Shatapatha Brahmana 4.5.5.9

4.5.5.9

atha yadajāḥ | kaniṣṭhāni pātrāṇyanu prajāyante tasmādetāstriḥ saṃvatsarasya vijāyamānā dvau trīniti janayantyaḥ kaniṣṭhāḥ kaniṣṭhāni hi pātrāṇyanu prajāyante

And because goats are produced after the fewest cups, therefore, though bringing forth thrice in a year, producing two or three, (they are) very few, for they are produced after the fewest cups.