One thing Waugh mentions in that excellent preface is this:
• It used to be believed by the vulgar that there were enough pieces of the ‘true cross’ to build a battleship. In the last century a French savant, Charles Rohault de Fleury, went to the great trouble of measuring them all. He found a total of 4,000,000 cubic millimetres, whereas the cross on which Our Lord suffered would probably comprise some 178,000,000. As far as volume goes, therefore, there is no strain on the credulity of the faithful.
Waugh’s figure of 178 million cubic millimeters, or 0.178 of a cubic meter, corresponds to a 12-foot upright post and a 6-foot crossbar, both cut from timber having a diameter of 8 inches. The sum total of the relics, stated as 4 million cubic millimeters, would be equivalent to a five-inch length of the same timber.