Valmiki Ramayana Bala Kanda Sarga 14 Shloka 20

तस्मिन् in that sacrifice, यूपोच्छ्रये in erecting sacrificial posts, प्राप्ते (सति) when the time, बैल्वा: bilva wood, षट् six, तथा and, बिल्वसहिता: along with bilva posts, तावन्त: as many, खादिरा: Khadira, तथा and, पर्णिन: च having leaves, अपरे some more posts, एक: one, श्लेष्मातकमय: made of Sleshmataka, तथा and, देवदारुमय: made of trees of Devadaru, तत्र there, द्वौ two, बाहुव्यस्तपरिग्रहावेव at a distance of two outstretched hands, विहितौ were erected.

When the time came to erect sacrificial posts, six posts, each made of bilva, khadira, parni, sleshmataka and two of devadaru wood, with a distance of two outstretched hands between them were erected.