Bengal observes a harvest festival known as Charak. It is believed that Charak has root in the pre-Aryan days and it was the most important social affair in Bengal before Durgapujo was introduced in the mid-18th century. Charak certainly borders on black magic, and aspires to drive out evil spirit from agrarian villages to assure a bumper crop. For seven days ordinary villagers go through different forms of penance, and on the very last day of the Bengali calendar (April 13th), Lord Shiva is believed to take hold of them. An old tree trunk-- known as Charak Tree-- is first worshipped by the womenfolk and then gets erected. More poles--with iron hooks hanging at extreme points-- are tied to the Charak tree and kept parallel to the earth. Every possessed villager is then pierced by another set of hooks and Shiva made them feel no pain. They are then hung from those ropes and people—by pulling on another rope—make them rotate around at breakneck speed. This rotation of the possessed ‘charak-sanyasi’ is for purification of the entire village.