Natyashastra
ध्रुवावर्णास्त्वलङ्कारा यतयः पाणयो लयाः । ध्रुवमन्योन्यसम्बद्धा यस्माद् तस्मात् ध्रुवाः स्मृताः ॥ ८॥
Words, syllables, embellishments, pauses, hand-beats, and tempo are all mutually connected in it; therefore it is known as a Dhruvā.
english translation
dhruvAvarNAstvalaGkArA yatayaH pANayo layAH । dhruvamanyonyasambaddhA yasmAd tasmAt dhruvAH smRtAH ॥ 8॥
hk transliteration by Sanscript