Stoney connections and more on the well. The ‘great flat stones’ call to mind Moss’s post below.
Adjoining the church is the chapel of St. Beuno. The passage to it is a narrow vault covered with great flat stones, and of far greater antiquity than either church or chapel; which seem nearly coeval. [...] In the midst is the tomb of the saint, plain, and altar-shaped. Votaries were wont to have great faith in him, and did not doubt but that by means of a night’s lodging on his tomb, a cure would be found for all diseases. It was customary to cover it with rushes, and leave on it till morning sick children, after making them first undergo ablution in the neighbouring holy well; and I myself once saw on it a feather bed, on which a poor paralytic from Meirioneddshire had lain the whole night, after undergoing the same ceremony.
From Tours in Wales by Thomas Pennant, written in the late 18th century. By the time the edition in the link was published in the 1880s, the tomb had gone.
There are some recent photos of Ffynnon Beuno at the super Well Hopper website.
Also, a link where you can read about the offerings of special bullocks with slits in their ears in depth: in Baring Gould’s ‘Lives of the British Saints‘ here.