"There is another wonder in Guyr - the altar, which is in the place, which is called Loyngarth, which is held up by the will of god. It seems better to me to narrate the history of that altar than to keep silent. But the fact is, while Saint Iltut was worshiping in the cave, which is next to the sea, which laps against the ground at the said place, (the mouth of the cave, also, is on the sea), and, behold, a ship was sailing towards him and two men sailing her and the corpse of a holy man was with them in the boat and the altar over the face of it, which was held up by the will of god and the man of god [Iltut] has advanced in their way and the corpse of the holy man and the altar remained inseparably above/before the face of the holy body. And they have said to saint Iltut: "that man of god has entrusted to us, in order that we might draw that person to you and we might bury him with you, and the name of him you may not reveal to any person, that men may not swear by him." Those two men returned to the ship and they have sailed. But that saint Iltut has established a church around/near the corpse of the holy man and around/near the altar and it continues all the time to this present day the altar is held up by the will of god. A certain minor king has come, in order that he might test, carrying a twig in his hand; he has formed a curve around the altar and he has held the twig by both hands from both sides and he has drawn it to himself in such a way the truth of that thing he has proved and that person afterwards during the month uninjured/untouched died. Another in truth [?for the truth] under the altar has looked and the sight of the eyes he has lost and before the month uninjured/untouched his life he has ended."1,2,3
This is the Wonder with something for everyone: magic, intrigue, death and - rarely for this wonder list, given its potential author was a monk - religion. Altars that floated on the sea were a stock element of celtic saint's lives in the Dark Ages and beyond, but this has the added mystery of a secret corpse (See Myth) and what must surely be the first description of what is known as the "hoop pass" in magic circles. Loyngarth in Guyr has been identified as Llwyngarth on the Gower, now Ystum-llwynarth or Oystermouth4,5. The saint in question is Saint Illtud. While neither the cave nor church have been identified, strong contenders include "Bob's Cave" on Mumbles Head6 and a chapel which may have been on Knab Rock or nearby (now destroyed)7. Despite this the wonder is commonly regarded as referring to the dolmen "Arthur's Stone" or Maen Cetti, some seven miles distant8. It seems much more likely it refers to a now-destroyed rock-arch which once stood by Knab Rock9.
You can read more on the Myth of Saint Illtud and moving stones, the Science of levitation, or visit details for the Gower sites and Knab Rock.