Natyashastra
अत्र श्लोकाः - ईषद्विकसितैर्गण्डैः कटाक्षैः सौष्ठवान्वितैः । अलक्षितद्विजं धीरमुत्तमानां स्मितं भवेत् ॥ ५॥
"With slightly expanded cheeks, accompanied by elegant glances and the use of sidelong glances, the Slight Smile (Smita) of the superior type is manifested, and it is observed in a dignified person who is not noticed by others."
english translation
atra zlokAH - ISadvikasitairgaNDaiH kaTAkSaiH sauSThavAnvitaiH । alakSitadvijaM dhIramuttamAnAM smitaM bhavet ॥ 5॥
hk transliteration by Sanscript