When archaeologists opened the digong in May 1987 they found not one relic but four, disposed through the crypt's chambers. One, yellowish and granular in texture, is venerated as the true bone, the ling gu or spirit bone; the other three are shadow bones, ying gu, two carved of jade and one of bone. Chinese scholarship reads the arrangement as a protective strategy: during the ninth-century persecutions of Buddhism the authentic relic could be hidden among convincing decoys, so that any confiscation or destruction might fall on a substitute.
Whether or not each object is what tradition claims, the four-relic set is itself a remarkable window on how medieval Buddhists thought about authenticity, substitution and the presence of the sacred in matter. The crypt also yielded a stone stele inventorying its contents, allowing the finds, some 2,500 objects of gold, silver, glass, ceramic and silk, to be matched against a Tang list, an unusually secure footing for an archaeological discovery of this importance.