Shiva Purana
अष्टत्रिंशन्मंत्ररूपा श्शिष्यदेहेऽथ मस्तके ॥ समावाह्य शिवं मुद्राः स्थापनीयाः प्रदर्शयेत् ॥ ३९ ॥
They are in the form of thirty-eight mantras on the body of the disciple and then on the head. Invoke Shiva and display the mudras to be placed.
english translation
aSTatriMzanmaMtrarUpA zziSyadehe'tha mastake ॥ samAvAhya zivaM mudrAH sthApanIyAH pradarzayet ॥ 39 ॥
hk transliteration by Sanscript