Shiva Purana
यज्ञदारुमयौ वापि स्मार्तौ वा शिल्पसम्मतौ ॥ पर्णे वा ब्रह्मवृक्षादेरच्छिद्रे मध्य उत्थिते ॥ २० ॥
They may be made of sacrificial wood or of smartas and may be approved by craftsmen. or on a leaf or in a hole in a brahma tree or other tree raised in the middle.
english translation
yajJadArumayau vApi smArtau vA zilpasammatau ॥ parNe vA brahmavRkSAderacchidre madhya utthite ॥ 20 ॥
hk transliteration by Sanscript