Most people don't know that the Holy Grail of medieval Arthurian Lore was not originally universally identified as the Cup of the Last Support, or linked to the Crucifixion. It's possible origins in the Cauldrons of Celtic mythologies will be a topic I'll possibly discus in the future.
The earliest Medieval Grail Romance of Chretien de Troyes describes it as a dish that contains a communion wafer. So if it had a Last Supper connection at all (which I'm not sure there was) it was probably to the Bread not the Wine.
Wolfram von Eschenbach’s Parzival (c. 1205 AD) which first describes the Grail in Book 9, describes it as a Stone of heavenly origin.
Graham Hancock in his book The Sign and The Seal makes much of the Grail being a stone rather then a Cup, and speculates that Wolfram's Grail is really code for the Ark being in Ethiopia, he then argues that Zazamanc is based on the Auxumite Kingdom. I haven't read Parzival in it's entirety so I don't know, but I don't think I've seen anyone but Hancock say Zaxamanc is where the Grail is in that work. (Rereading it I remembered the gist was he saw the Gail Maiden marrying Feirefiz was a coded way of saying it went to Zazamanc). None the less Hancock's theory has remained interesting enough to me that it influenced the previous Arthurian Legend post I did on this blog.
Bob Cornuke also argues for the Ark being in Ethiopia but coming there a different way then the Menelik Legend, and unlike Hancock does so as a Bible Believing Christian, but doesn't bring the Grail theory into it that I can recall. I don't agree with any of Hancock's other alternative history theories, but The Sign and The Seal I highly recommend, it's a fun book even if you disagree. I agree with all Cornuke's theories but his latest Temple one.
Back to the subject at hand, Hancock does mention the Heavenly origin of the Grail aspect of Wolfram, he goes into a theory about the Tablets in the Ark actually being one of many Meteorites that fell to Earth and became objects of worship (like Acts 19:35, or the Kaaba in Mecca). .But he doesn't reveal the full story of Wolfram's description.
“They who took no part in the conflict, when Lucifer would fight with Three-in-One, those angels were cast forth from Heaven’s height. To the earth they came, at God’s bidding, and that wondrous stone did tend” (translation: Jesse L. Weston)It’s possible, given the attribution of the Grail myth to Arabic texts, that Wolfram had in mind the alleged alchemical power of the Emerald Tablet, also from Arabic texts, when describing the Holy Grail as essentially the Philosopher’s Stone.
This, in turn, ties in with a legendary set of songs supposedly composed by bards which included Wolfram, called the Wartburgkrieg, composed at least fifty years later. In the surviving accounts, one of the poems told how Lucifer’s crown had a stone that fell to earth thanks to Michael:
“Sixty thousand angels who wished to drive God from heaven had a crown made for Lucifer. When the archangel Michael tore this from Lucifer’s head, a stone sprang loose from it, and that stone is the Grail” (translation: William Ashton Ellis).This, in turn derived from the medieval myth that Venus, the Morning Star, was the jewel from Lucifer’s crown. Many writers fail to distinguish between this poem and Parzival, and some writers mistakenly attribute these lines to Parzival.
In 1832, “San Marte” (Albert Schulz) produced a loose paraphrase of Wolfram in which he interpolated the Wartburgkrieg text without indicating the distinction. He falsely makes Wolfram say....
"The holy Grail is a stone of the most wondrous and mysterious kind. A number of angels having remained neutral and inactive during the battle of Lucifer and the rebel angels against God and the faithful heavenly hosts, after Lucifer’s fall they were condemned by God to support this stone, which had dropped from Lucifer’s crown, hovering between Heaven and Earth till the hour of redemption of sinful mankind. Then they brought it to Earth, and, formed into a costly vessel, it served for the dish out of which Christ ate the Pascal lamb, and in which Joseph of Arimathea received the Saviour’s blood." (translation: William Ashton Ellis)Wolfram’s version stops at “support this stone.” Everything after is Schulz’s text. Victorian authors repeated this rather than bother to read the original (which, being medieval German they could not), and thus Wolfram became retroactively the originator of the claim of Lucifer’s crown. Modern people know the story because of glosses and notes on Wagner, using these Victorian sources, interpolated into editions of Parsifal. Tolkien I'm certain however had a better handle on German then Victorian writers, but could still have been influenced by all of this.
In The Silmarilion, The Silmarils are three Jewels forged by Feanor to contain the Light of the Two Trees of Valinor. After the Trees were destroyed by Morgoth formally known as Melkor they became all that remained of the Light, and they fell into Morgoth's possession who had them placed in his massive Crown.
Many Wars were fought over the Silmarils. Eventually one was taken from Morgoth's Crown by Luthien and Beren. It inevitably entered the possession of their descendant Elwing. Elwing married Earendil (name means Evening Star, Tolkien took it form the Norse Aurvandil) son of Tour and Idril, and eventually her Silmaril became the Jewel of his ship Vingilot, which was granted by the Valar the ability to fly though the Heavens.
In Tolkien's Cosmology, Venus is the Star of Earendil, (because Venus is also known as the Evening Star as well as the Morning Star), which is defined as the Light of The Silmaril. In Greek Heosphorus/Eophorus (the name used in the Septuagint of Isaiah 14) is the Morning Star and Hesperus the Evening Star, later Greco-Roman writers like Cicero became aware the two were the same star.
The other two Silmarils were eventually taken by the Sons of Feanor after Morgoth fell but led to their deaths. One was cast into The Earth (leading to debatable theories of it being the Arkenstone) and the other into The Sea, where I'd be very interested in Fan Fiction based on it being found by Captain Nemo and the Nautilus. I can't be the first to think of that idea?
So the gist is, I think it's highly probable this obscure esoteric alternate Grail tradition partly helped inspire Tolkien.