In this parish [Llanfihangel Genau'r-glyn] are several remains of Druidical structures. The most remarkable is that generally called Gwely Taliesin, or Taliesin's bed. This is Taliesin ben beirdd, mentioned before in this work, and who flourished about the year 540; but on attentively considering this structure, we shall readily pronounce such an account to be wholly fabulous. The popular supestition respecting this, is that should any one sleep in this bed for one night, he would the next day become either a poet, or an idiot. A large heap of earth has been raised, and surrounded by two circles of stones, the innermost of which is twenty-seven feet in diameter, and the outer one about thirty-one feet. In the centre of this is the gwely, which is composed of six stones, five placed so as to make an oblong chest, and another for its cover. The covering stone has been taken off, and thrown on one side, and measures upwards of six feet in length, and three feet six inches in width. The chest itself is three feet in depth, six feet long, and two feet three inches broad. In this chest was, many years ago, found a human skull; therefore, whether this was a cromlêch, and the skull that of a victim sacrificed, or the sepulchral tumulus of an Arch Druid, and this the remains of his reverend head, is a subject for conjecture. That it was not the grave of Taliesin, we may collect from the following considerations. He flourished when Christianity had taken deep root in Wales, and his works throughout evince his sincere belief in the Christian doctrines. It was the custom, after the introduction of Christianity into Britain, to make frequent use of the cross, and this emblem was always carved on the sepulchral monuments of devout persons of that period, as we have many examples even in this country. As Taliesin therefore was celebrated as a pious Christian, as well as an excellent poet, such a monument would undoubtedly be erected to him, and probably was in North Wales, where he spent the latter part of his life. This druidical relic is situated on a mountain, called Pen Sarn ddu, between the rivers Ceulan and Clettwr.
Meyrick, Cardiganshire (1808), 432-3
We also have a longer extract
from Meyrick about the parish.