I'm wondering if this account is speaking of the destruction of the same monument:
At Mayborough they dug up a brass celt. On the other side of the Eimot, upon a high ground overlooking all, is a very fine round tumulus, of a large size, and set about with a circle of stones: this in all probability was the funeral monument of the king that founded the temple and circus. Someone has lately been digging away part of the barrow, and carried off some of the stones, and demolished others.
Later in the same text, Stukeley adds:
The great barrow accompanied with stones, by the Eimot side, is called Haransley hill.
This circle was described by Pennant in his 18th century Itinary of Scotland & Northern England. he described the site as a large circle of grit stones about 60ft in diameter surrounding a vast cairn of stones. Pennant located the site to opposite Mayburgh on the other side of the Eamont. Waterhouse says that this would place the circle in the southern outskirts of Penrith.
The OS grid reference supplied here comes from the Cumbria County Councils Historic Environment Record.