Well, sir, you have been hoist by your own petard, there. Indeed, the Grail could never have come from the Holy Land to your house--not even if Perceval, or Saint Clair himself, had borne it--if this were a one dimensional universe. For your house was never extant when they had it, nor anywhere near where they had it when it finally showed up. So two dimensions is clearly your minimum, even if they walked over the waters and straight to Idaho, which no-one in their right mind would want to do.