Shiva Purana
शंखमुद्रां च पुरतश्चतुरस्रं प्रकल्पयेत् ॥ तदन्तरेर्द्धचन्द्रं च त्रिकोणं च तदन्तरे ॥ ४ ॥
The conch and the mudra should be placed in front of the square. There is a half moon in the middle of it and a triangle in the middle of it.
english translation
zaMkhamudrAM ca puratazcaturasraM prakalpayet ॥ tadantarerddhacandraM ca trikoNaM ca tadantare ॥ 4 ॥
hk transliteration by Sanscript