The precise origin of pearling is unknown, but early documentation in China indicates that it had been imported from Southeast Asia no later than the early s. Once inside, the penis becomes erect and cannot be withdrawn until it is limp. Pearling is performed in prison by the Yakuza, with each pearl supposedly symbolizing a year spent in prison. From Wikipedia, the free encyclopedia. In the middle of the bolt is a hole, through which they urinate. As the boys grew older, these pins would be decorated and they would later fasten bluntly spiked rings for the stimulation of their sex partners.