Grail, The Holy, the cup or vessel, said to have been made of an emerald stone, that was used by Christ at the Last Supper, and in which Joseph of Arimathea caught up the blood that flowed from His wounds on the Cross; it was brought to England by Joseph, it is alleged, but after a term disappeared; to recover it formed an object of quest to the Knights of the Round Table, in which Sir Galahad succeeded, when it was seen by certain other knights, but it has not been seen since, for none is permitted to see it or can set eye on it but such as are of a pure heart.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Graiæ * Gramont