Natyashastra
न मार्गभेदोऽक्षरेषु कश्चिदप्युपपद्यते । वर्णमात्रा द्विगुणिताद्वर्णभेदः प्रकीर्तितः ॥ ११५॥
No change of the Mārga, is available as regards the syllables ॥ indicated by the name of Tālas ॥. It is only due to doubling the Mātrā that the variation of Varṇas has been described.
english translation
na mArgabhedo'kSareSu kazcidapyupapadyate । varNamAtrA dviguNitAdvarNabhedaH prakIrtitaH ॥ 115॥
hk transliteration by Sanscript