Natyashastra
छन्दोक्षरपदानां हि समत्वं यत्प्रकीर्तितम् । कलाकलान्तरकृतः स लयो मानसञ्ज्ञितः ॥ ३३२॥
The evenness of syllables and words in metre, produced by the alternation of kalās (time-units and sub-units), is called mānasa laya — the mental or internal rhythm.
english translation
chandokSarapadAnAM hi samatvaM yatprakIrtitam । kalAkalAntarakRtaH sa layo mAnasaJjJitaH ॥ 332॥
hk transliteration by Sanscript