According to later Grail tradition, beginning with the texts of Robert de Boron, the Grail was the chalice or dish used by Christ at the Last Supper (and later used by Joseph of Arimathea to catch Christ’s blood on the Cross).
Biblical tradition holds that Christ and his disciples used a round table for the Last Supper, which inspired Joseph’s Grail Table and Arthur’s Round Table.
Joseph d’Arimathie | Robert de Boron, 1191-1202
Vulgate Estoire del Saint Graal | 1220-1235
Vulgate Queste del Saint Graal | 1215-1230