From the city of Murias the Tuatha De Danann brought the Coire Anseasc, the Cauldron of the Dagda, the Irish All-Father. It is said that:
"no company ever went away from it unsatisfied."[The Lebor Feasa Runda, 2008, Steven L. Akins]
This reminds me of what is said about the Holy Gral that it was able to produce precious food for the knights who guarded it. The Gral is portrayed as a sacred stone in Wolfram von Eschenbach`s Parzival but it is also portrayed as a cup in other mediaeval literature. I believe that these two different concepts, the stone and the cup which are both perceived as being the Gral are in fact two different objects that have become confused into one single concept. The Anglo-Saxon Futhorc`s Gral Runes, Calc, Stan and Gar reflect both the stone and the cup version of the Gral as do the Four Hallows of the Tuatha De Danann, the stone, spear, sword and the cauldron. The confusion was brought about by the attempted xtianisation of what in fact are Indo-European concepts.
Cauldrons are very common in Celtic and Germanic mythology and usually have special life enhancing or life endowing powers attributed to them. A cauldron features in Hymiskvida where Thor and Tyr set off on an adventure to obtain a huge cauldron from the giant Hymir for the brewing of mead for a feast of the Gods, to be hosted by Aegir.
There is of course the famous Gundestrup Cauldron discovered in 1891 in a Danish peat bog. It is made of silver and is dated to have been made sometime between 200BCE and 300CE. Its decoration is conjectured to be either Celtic or Thracian symbolism. This may originally have belonged to a Celtic tribe living south of the River Elbe and subsequently looted by the Cimbri and taken to Denmark. The cauldron may in fact be a combined cultural product of Celts, Teutons and other Indo-European tribes. The imagery on one of the plates suggests that a God is reviving a warrior by immersing him into a cauldron.
The life giving, life enhancing and nourishing powers of Parzival`s Gral clearly are an echo of ancient Germanic and Celtic religious belief and have nothing to do with the xtian religion. What xtianity could not destroy in Northern Europe it plagiarised-a common trait of Abrahamic religions.
"Some may be confused to some extent by what seems to be the Christian symbolism of the Grail-however, the astounding fact is that there was originally nothing Christian about it."[ALU An Advanced Guide to Operative Runology, Edred Thorsson, 2012]
The Gral as a cup or chalice is figured in the Calc rune. Thorsson discusses in ALU how the heathen Germanic sacred drinking vessel of the horn was xtianised into a cup or chalice. Horns from the aurochs were used for both sacred and profane drinking. The golden horns of Gallehus are a glorious and typical example of the sacred nature of the drinking horn.
"Horns were even used in the early Germanic church in place of the Romano-Christian chalice-a practice outlawed by the church."[ALU]
The word calc apparently is a borrowing from Latin but in Old Norse it is known as kalkr, `chalice` which can also be used in a heathen context. So the word calc and the obvious horn shape of the rune stave make it very clear what it is supposed to represent.
Nigel Pennick in Wyrdstaves of the North  states:
"This rune has the literal meaning of a ritual container or an offering cup, such as the maple-wood Wassail bowl used in the rites of Yuletide, and the spiritual vessels in Celtic and Christian mythology, such as the Cauldron of Wisdom and the Holy Grail."
He believes that the rune can be used magically to contact the dead. If one considers also how it resembles a tree with three roots and how these go down into the underworld it certainly does have this connotation. We should also remember how Woden deposited His eye in Mimir`s well in order to acquire wisdom and the well could also be thought of as a cauldron of inspiration.
It is interesting to note that a special golden cauldron resembling the Gundestrup Cauldron was made for the SS and was possibly used in rites carried out at Schloss Wewelsburg. This was later deposited in the Chiemsee in Bavarian in the closing days of WWII and recovered by divers in 2001.