This relic is reputedly the wood of the cross on which Jesus Christ was crucified.
Legend has it that the True Cross was found by St. Helena, mother of Constantine the Great, during her pilgrimage to the Holy Land about 326. The earliest historical reference to veneration of the True Cross occurs in the mid-4th century.
Over the years many critics of these relics claimed there were enough relics of the Cross to build an entire ship! However, theologians claimed that the blood of Christ gave to the True Cross a kind of material indestructibility, so that it could be divided indefinitely without being diminished.
In 1870, a Frenchman, Rohault de Fleury, catalogued all the relics of the True Cross, including relics that were said to have existed but were lost. He measured the existing relics and estimated the volume of the missing ones. Then he added up the figures and discovered that the fragments, if glued together, would barely have made up more than one-third of a cross.
The problem wasn’t that there was too much wood – it was that most of the True Cross, after being unearthed in Jerusalem in the fourth century, was lost again!