Natyashastra
कलिकं मध्यमे यत्र नीचेष्वर्धकलं भवेत् । एवमर्धार्धहीनं तु जडानां सम्प्रयोजयेत् ॥ ३३॥
Where the gait of the middling is one Kalā, that of the inferior should be half a Kalā; thus, half and quarter measures are applied for the dull or heavy characters.
english translation
kalikaM madhyame yatra nIceSvardhakalaM bhavet । evamardhArdhahInaM tu jaDAnAM samprayojayet ॥ 33॥
hk transliteration by Sanscript