Māṇḍūkī Śikṣā 62

62

svaraḥ uccaḥ svaro nīcaḥ svaraḥ svarita ucyate
vyañjanānyanu varttante yatrāsau tiṣṭhati svaraḥ

The high tone, the low tone, [and] the tone is called circumflex accent; / consonants follow where that tone stands.