Natyashastra
त्रेताग्निसंस्थिता मध्या तर्जन्याङ्गुष्ठका यदा । काङ्गुलोऽनामिका वक्रा यदाश्चोर्ध्वा कनीयसी ॥ ८८॥
Kāṅgula—The middle and the fore-fingers and the thumb to be separated and the ring finger to be bent but the little finger raised.
english translation
tretAgnisaMsthitA madhyA tarjanyAGguSThakA yadA । kAGgulo'nAmikA vakrA yadAzcordhvA kanIyasI ॥ 88॥
hk transliteration by Sanscript