Shiva Purana
वाचिकस्त्वेक एव स्यादुपांशुः शतमुच्यते ॥ साहस्रं मानसः प्रोक्तः सगर्भस्तु शताधिकः ॥ २९ ॥
If the efficacy of the Vācikajapa is one, that of the Upāṃśu Japa is hundred; that of the Mānasajapa is a thousand; that of the Sagarbha Japa is hundred times more.
english translation
vAcikastveka eva syAdupAMzuH zatamucyate ॥ sAhasraM mAnasaH proktaH sagarbhastu zatAdhikaH ॥ 29 ॥
hk transliteration by Sanscript