Needless to mention that this Mantra Experiment is only for experienced Sadhaks, Upasaks and Yogis who are well-versed with such fearsome rituals.
The Mantra Experiment has to be started on a Saturday Night in a Smashan Bhoomi[Hindu Crematorium] or in an Islamic Kabrastan or Christan Graveyard or any other similar place, which is meant for the purpose of burying or cremating dead bodies of human beings.
The Sadhak has to sit down on a Woolen Sitting Mat and place a Tribhujakaar or Triangular Havan Kund made from Copper in-front of him and light the Havan.
After this, he should light 4 Char Mukhi Diyas on the 4 direction, outside the Havan Kund.
Then, he should chant 1 Mala or 108 Repetitions of the Bhuteshwar Mantra using a Rudraksha Japa Mala, while offer Sabut Urad Dal, Black Sesame Seeds and Sesame Seed Oil to the Havan.
The Tantra says that Bhuteshwar appears after the conclusion of the Mantra Chanting and when he manifests, the Sadhak should offer a little bit of Blood from his Anamika Finger[Ring Finger] to the Havan. This is said to appease Bhuteshwar and he fulfills any specific wish or desire of the Sadhak.
ॐ वं वं भूं भूतेश्वरा मम वश्यं कुरु कुरु स्वाहा ||
Om Vam Vam Bhoom Bhooteshwara Mam Vashyam Kuru Kuru Swaha ||
A Variation of the same Mantra, published a few years back, can be seen here - Ghost Control and Enchantment Mantra