Natyashastra
तेषां समासतो योगः करणेषु विभाव्यते । प्रायेण करणे कार्यो वामो वक्षःस्थितः करः ॥ १७१॥
The combination of these ॥ movements॥ is generally evident in the Karaṇas. In most Karaṇas, the left hand is positioned on the chest.
english translation
teSAM samAsato yogaH karaNeSu vibhAvyate । prAyeNa karaNe kAryo vAmo vakSaHsthitaH karaH ॥ 171॥
hk transliteration by Sanscript