Sutra of the Supreme Root Teachings Spoken by the Buddha: Volume Two
Chapter Six: Ritual Procedures for the Vetalī Seal Accomplishment and Invocation
Furthermore, the Yamantaka Vidyaraja's fundamental seventeen-syllable great mantra, called the Vetali Secret Heart Seal, can cause great joy in the Yamantaka Great Fearless Vidyaraja. The mantra holder, whether in a place of confinement or a charnel ground and other such locations, if they recite it with direct presence, will certainly attain accomplishment. This Vetali seal method was spoken by the Yamantaka Vidyaraja himself.
Cross the two middle fingers, tuck the two ring fingers into the palm, bend the two index fingers like hooks, place the two thumbs on top of the little fingers, then reverse and extend the two thumbs. This is the Vetalī mudrā method—true, not false, and possessing great power.
At that time, the mantra-holder, within the Haha-bhūta maṇḍala, recites the seventeen-syllable great mantra according to the method, using this Vetalī mudrā. All desired accomplishments can be granted.
Now, the wrathful maṇḍala is explained. As in the previous Bhr̥kuṭa-maṇḍala, make it square with four sides and four corners, exactly one cubit in width—neither more nor less. At each of the eight directions, light a fire. At the four gates of the maṇḍala, place a skull, and on each skull, place a vetāla. In the center of the maṇḍala, also place a vetāla, with disheveled hair. Additionally, arrange a garland of vetālas, following the ritual procedure of the previous Bhr̥kuṭa-maṇḍala.