Yāska's Nirukta 7.12

7.12

mantrā mananāt/
chandāṃsi chādanāt/
stomaḥ stavanāt/
yajus yajateh/
sāma sammitam ṛcā,.asyater vā,.ṛcā samam menea iti naidānāh/[782]
gāyatrī gāyateḥ stuti karmaṇas,.tri gamanā vā viparītā.''.gāyato mukhād udapatat''.iti ca brāhmaṇam/[782]
usnik utsnātā bhavati snihyater vā syāt kānti karmaṇah,.usnīsinī[furṇishied witḥ a turban].vā ity aupamikam[comparatively]/[782]
usnīsam snāyateh/[782]
kakubḥ kakubhinī bhavati/
kakubḥ ca kubjaś ca kujater vā ubjater vā/[782]
anustubḥ anustobhanād.''.gāyatrīm eva tripadām satīm caturthena pādena anustobhati''.iti ca brāhmaṇam/[783]
bṛhatī paribarhanāt/[782]
paṅktiḥ pañcapadā/[782]
tristubḥ stobhaty uttara padā/
kā tu tritā syāt,.tīrṇatamaṃś chandas,.trivṛt vajras tasya stobhanī iti vā/[782]
``yat trir astobhat tat tristubhas tristubḥ tvam''.iti vijñāyate/[783]