Kaushitakagrihyasutra 3.3.5

3.3.5

mahāvyāhṛtayaścatasraḥ \ vāstoṣpate iti catasraḥ \ vāstoṣpate dhruvā sthūṇā sauviṣṭakṛtī daśamī sthālīpākasya rātrau \5\

There are four great mystical utterances; four [verses beginning with] 'O Vāstoṣpati'; 'O Vāstoṣpati, a firm post…'; the tenth is the Sviṣṭakṛt verse, for the boiled sacrificial mess at night.