“When Merlin established the Round Table, he said that the truth of the Holy Grail, at that time a secret, would eventually be made known through the members of the Round Table. When he was asked how one could recognize the most worthy participants, he answered, ‘Three questers will succeed: two of them virgins and the third one chaste. One of the three will surpass his father just as the lion surpasses the leopard in strength and courage. He will become the master and pastor of all the others. Until Our Lord sends this man among them with a suddenness that will take them by surprise, the members of the Round Table will waste their time searching for the Holy Grail.’

“When the people heard this they said, ‘Merlin, since by your account this chosen one will be so extraordinarily valiant, you should create a special seat destined for him alone and make it much larger than the others, so it will be easily recognized.’

“‘I will do that,’ said Merlin. And he fashioned a large and wonderful seat among the others and then kissed it, saying he had done this for the love of the Good Knight who would sit there.

‘Then the others asked, ‘Merlin, what will happen to this seat?’

“‘Indeed,’ he replied, ‘many amazing things. No one will sit here without being killed of maimed until the True Knight takes his place on this seat.'

“‘So anyone attempting to sit there runs a great risk?’ they asked.

“‘A perilous risk,’ said Merlin. ‘And for that reason the seat will be called the Perilous Seat.’”

Vulgate Quest for the Holy Grail