Garudapurana 1.207

The glorious Garuḍa Mahāpurāṇa: 207
Sūta said:
Bowing to Vāsudeva the guru, Gaṇa, Śambhu, and Sarasvatī,
I shall explain metre divided by mātrās and syllables for one of small intellect.

The triplets of metrical feet are mnau, bhyau, jrau, stau, with a long and short syllable at all, beginning, middle, and end.
An āryā has four mātrās; the four feet have them at the beginning, end, throughout, and middle.

Ending in a consonant, ending in a visarga, long, followed by a conjunct, and with an anusvāra is heavy (guru);
at the end of a line it may be either; it is said to have two mātrās.

Even when there is no conjunct sequence, a heavy syllable may sometimes have lightness.
It is designated as a śloka, an āryā, and so on; a caesura is called a pause (yati).

A foot (pāda) should be known as a fourth part; even is called 'sama', uneven is called 'viṣama'.
Metres are even (sama), half-even (ardhasama), and uneven (viṣama) as the third.

Thus ends the two hundred and seventh chapter, named 'Exposition of the Definitions and Rules of Metre' in the treatise on metres in the section on conduct of the first part of the glorious Garuḍa Mahāpurāṇa.