Natyashastra
उत्साहाध्यवसायाभ्यामधोमुखविचिन्तनैः । शिरःप्रकम्पस्वेदाद्यैस्तं प्रयुञ्जीत पण्डितः ॥ ७९॥
It is to be represented on the stage by energy, determination, reflection with a downcast face, shaking the head, perspiration and the like.
english translation
utsAhAdhyavasAyAbhyAmadhomukhavicintanaiH । ziraHprakampasvedAdyaistaM prayuJjIta paNDitaH ॥ 79॥
hk transliteration by Sanscript