A uniquely prestigious use of porphyry was its choice as material for imperial sarcophagi in the 4th and early 5th centuries CE. That tradition appears to have been started with Diocletian's porphyry sarcophagus in his mausoleum, which was destroyed when the building was repurposed as a church but of which probable fragments are at the Archaeological Museum in Split, Croatia. The oldest and best-preserved ones are now conserved at the Vatican Museums and known as the Sarcophagi of Helena and Constantina. Nine others imperial porphyry sarcophagi were long held in the Church of the Holy Apostles in Constantinople. They were described by Constantine VII Porphyrogenitus in the "De Ceremoniis" (mid-10th century CE), who specified them to be respectively of Constantine the Great, Constantius II, Julian, Jovian, Theodosius I, Arcadius, Aelia Eudoxia, Theodosius II, and Marcian. Of these, most still exist in complete or fragmentary form, despite depredations by later Byzantine Emperors, Crusaders, and Ottoman conquerors. Four presently adorn the facade of the main building of the İstanbul Archaeology Museums, including one whose rounded shape led Alexander Vasiliev to suggest attribution to Emperor Julian on the basis of Constantine Porphyrogenitus's description. Vasiliev conjectures that the nine imperial sarcophagi, including one which carries a "crux ansata" or Egyptian cross, were carved in Egypt before shipment to Constantinople.