Natyashastra
चतुर्थकारः पूजां तु स कृत्वान्तर्हितो भवेत् । ततो गेयावकृष्टा तु चतुरश्रा स्थिता ध्रुवा ॥ १०२॥
The fourth performer, after completing the worship, should withdraw. Then, the fixed note (Dhruvā) should be extended through the Geya and assume a four-sided formation.
english translation
caturthakAraH pUjAM tu sa kRtvAntarhito bhavet । tato geyAvakRSTA tu caturazrA sthitA dhruvA ॥ 102॥
hk transliteration by Sanscript