Natyashastra
चतुरश्रा ध्रुवा तत्र तथा द्रुतलयान्विता । चतुर्भिस्सन्निपातैश्च कला ह्यष्टौ प्रमाणतः ॥ १२५॥
The square is fixed there, and is endowed with a rapid measure, with four placements; the art is thus eightfold in measure.
english translation
caturazrA dhruvA tatra tathA drutalayAnvitA । caturbhissannipAtaizca kalA hyaSTau pramANataH ॥ 125॥
hk transliteration by Sanscript