Shiva Purana
ततश्च देशिकस्तस्य दर्भैराच्छाद्य मस्तके ॥ मण्डलस्थेशदिग्भागे चतुरस्रं प्रकल्पयेत् ॥ ३४ ॥
Then the desika covered his head with darbha grass A square should be placed in the direction of the Lord in the circle.
english translation
tatazca dezikastasya darbhairAcchAdya mastake ॥ maNDalasthezadigbhAge caturasraM prakalpayet ॥ 34 ॥
hk transliteration by Sanscript