Shiva Purana
तत्र सावरणं वापि निरावरणमेव वा ॥ द्विदले षोडशारे वा द्वादशारे यथाविधि ॥ ६३ ॥
There may be a covering or a covering without a covering. They may be placed in two or sixteen or twelve leaves according to the prescribed method.
english translation
tatra sAvaraNaM vApi nirAvaraNameva vA ॥ dvidale SoDazAre vA dvAdazAre yathAvidhi ॥ 63 ॥
hk transliteration by Sanscript