सानुस्वारश्च दीर्घश्च विसर्गी च गुरुर्भवेत् ।
वर्णसंयोगपूर्वश्च तथा पादान्तगोऽपि वा ॥
sānusvāraś ca dīrghaś ca visargī ca gurur bhavet |
varṇa-saṁyoga-pūrvaś ca tathā pādāntago’pi vā ||
(Chando-mañjarī: 1.11; cited in the Hari-nāmāmṛta-vyākaraṇa Amṛta-ṭīkā: 1.81)
“A vowel with an anusvāra (ṁ), a dīrgha (trivikrama) vowel, a vowel with a visarga (ḥ), and a vowel [immediately] prior to a conjunct (sat-saṅga) of varṇas is guru (“heavy”), and so too optionally is a vowel coming at the end of a pāda [i.e. a line or quarter of a verse].”