Natyashastra
चतुष्कादौ चतुर्मात्रा यथोक्तगुरुलाघवाः । यथायोगं गणाः कार्या गीतेष्वासारितेषु च ॥ ११२॥
In [ the Tāla of ] the Āsārita songs, one should make its [ Kalā ] of four etc., consist of gaṇas made up of four mātrās, their long and short syllables being as prescribed before.
english translation
catuSkAdau caturmAtrA yathoktagurulAghavAH । yathAyogaM gaNAH kAryA gIteSvAsAriteSu ca ॥ 112॥
hk transliteration by Sanscript