Natyashastra
द्विकला च पुनः शम्या तालो द्विकलश्च कर्तव्यः ॥ १५८॥
Then again there should be a Śamyā of two Kalās, followed by a Tāla of two Kalās.
english translation
dvikalA ca punaH zamyA tAlo dvikalazca kartavyaH ॥ 158॥
hk transliteration by Sanscript