Natyashastra
गुर्वादिस्तु गुरुः कार्यो लघ्वादिश्च लघुस्तथा ये त्वोजच्छन्दसां युक्ता ज्ञेया ते क्षेपिकी तथा यान्योजयुग्मछन्दांसि ज्ञेयान्याक्षेपिकी तथा । लघुयुग्मकृता याऽस्या स्थिता साऽऽक्षेपिकी भवेत् ॥ ४३॥
A metre beginning with a long syllable should be employed in the Sthitā Dhruvā, and likewise one beginning with a short syllable should be employed in the Drutā Dhruvā. Those metres which are associated with vigorous (ojaḥ) movement are to be known as belonging to the Ākṣepikī Dhruvā. Metres consisting of paired arrangements (yugma) are likewise to be regarded as applicable to the Ākṣepikī Dhruvā. That metre which is formed with pairs of short syllables in the Sthitā becomes the Ākṣepikī Dhruvā.
english translation
gurvAdistu guruH kAryo laghvAdizca laghustathA ye tvojacchandasAM yuktA jJeyA te kSepikI tathA yAnyojayugmachandAMsi jJeyAnyAkSepikI tathA । laghuyugmakRtA yA'syA sthitA sA''kSepikI bhavet ॥ 43॥
hk transliteration by Sanscript