Shiva Purana
लिंगं पीठं चरे त्वेकं लिंगं बाणकृतं विना । लिंगप्रमाणं कर्तृ-णां द्वादशांगुलमुत्तमम् ८ ।
Save the one which the asura Bāṇa worshipped, both the emblem and the seat shall be unitary, if emblem be mobile. The length of the emblem shall be of the measure of twelve fingers of the devotee.
english translation
liMgaM pIThaM care tvekaM liMgaM bANakRtaM vinA । liMgapramANaM kartR-NAM dvAdazAMgulamuttamam 8 ।
hk transliteration by Sanscript