Shiva Purana
पश्चात्प्रणवविद्धीमान्प्रणवन्यासमाचरेत् ॥ बाहुद्वये कूर्परयोस्तथा च मणिबन्धयोः ॥ ३७ ॥
Afterwards, one who knows the oṁkāra should chant the oṁkāra. On both arms, on the torso, and on the wrists.
english translation
pazcAtpraNavaviddhImAnpraNavanyAsamAcaret ॥ bAhudvaye kUrparayostathA ca maNibandhayoH ॥ 37 ॥
hk transliteration by Sanscript