Shiva Purana
अष्टोत्तरशतं जप्त्वा द्विषड्वारं तु तर्पयेत् ॥ पुनराचम्य विधिवत्प्राणायामत्रयं चरेत् ॥ ३२ ॥
After performing the Japa of Gāyatrī hundred and eight times, he shall offer Tarpaṇa twelve times. After performing the Ācamana he shall perform Prāṇāyāma thrice.
english translation
aSTottarazataM japtvA dviSaDvAraM tu tarpayet ॥ punarAcamya vidhivatprANAyAmatrayaM caret ॥ 32 ॥
hk transliteration by Sanscript