Māṇḍūkī Śikṣā 60

60

nanu dhārayet vṛttamupasparśamupodāttaṃ nipātayet
ekākṣare dhārayenna ca dhṛtamuccārayet svare vāpi

Indeed, one should hold the tempo, drop the light contact, [and] lower the sub-acute; / on a single syllable one should hold [it], and one should not utter what is held in a tone or [the like].