One verse

Srimad Bhagavatam 11.14.34

11.14.34

हृद्यविच्छिन्नमोङ्कारं घण्टानादं बिसोर्णवत् । प्राणेनोदीर्य तत्राथ पुन: संवेशयेत् स्वरम् ॥ ३४ ॥

hṛdy avicchinam oṁkāraṁ ghaṇṭā-nādaṁ bisorṇa-vat prāṇenodīrya tatrātha punaḥ saṁveśayet svaram

hṛdi
in the heart
avicchinnam
uninterrupted, continuous
oṁkāram
the sacred vibration om
ghaṇṭā
like a bell
nādam
sound
bisa-ūrṇa-vat
like the fiber running up the lotus stalk
prāṇena
by the wind of prāṇa
udīrya
pushing upward
tatra
therein (at a distance of twelve thumb-breadths)
atha
thus
punaḥ
again
saṁveśayet
one should join together
svaram
the fifteen vibrations produced with anusvāra.

Beginning from the mūlādhāra-cakra, one should move the life air continuously upward like the fibers in the lotus stalk until one reaches the heart, where the sacred syllable om is situated like the sound of a bell. One should thus continue raising the sacred syllable upward the distance of twelve aṅgulas, and there the oṁkāra should be joined together with the fifteen vibrations produced with anusvāra.