Siege Perilous
In Thomas Malory's 1485 book "Le Morte d'Arthur" , in an account taken from the Vulgate "Queste del Saint Graal" , the newly knighted Sir Galahad takes the seat in Camelot on Whitsunday , 454 years after the death of Jesus . 
<triplet> Le Morte d'Arthur <subj> Thomas Malory <obj> author <subj> 1485 <obj> publication date