Natyashastra
बाहुशीर्षे प्रसन्ने च नात्युत्क्षिप्ते च कारयेत् । ग्रीवाप्रदेशः कर्तव्यो मयूराञ्चितमस्तकः ॥ ५॥
The region of the shoulders and head should be kept at ease and not excessively raised; the neck should be held in a manner with the head gracefully bent like that of a peacock.
english translation
bAhuzIrSe prasanne ca nAtyutkSipte ca kArayet । grIvApradezaH kartavyo mayUrAJcitamastakaH ॥ 5॥
hk transliteration by Sanscript