Natyashastra
नानाभावसमायुक्तस्तथा च शयनाश्रयः । विष्कम्भिताञ्चितौ पादौ त्रिकं किञ्चित्समुन्नतम् ॥ २०३॥
Associated with various emotional states, and similarly applicable to lying down, ॥ the sitting posture involves॥ the two feet kept apart and slightly bent, the region of the hips (Trika) slightly raised.
english translation
nAnAbhAvasamAyuktastathA ca zayanAzrayaH । viSkambhitAJcitau pAdau trikaM kiJcitsamunnatam ॥ 203॥
hk transliteration by Sanscript