Falling into conversation with [Mr Maclean] on the subject of cairns, he informed me, there was only one in the whole island, called Cairn mich Re, signifying the cairn, or tomb, of the king's son. I thought this would be a very favourable opportunity.. of opening one of these cairns; and expressing a wish to that effect, Mr. Maclean informed me he had often thought of doing it himself, and if I pleased, we would set out for the spot immediately..
.. It is situated [by the roadside] near the village of Grissipol.. We soon fell to work.. While we were thus employed, a venerable figure, with hairs as white as snow, came slowly up to the cairn, shaking his head, and muttering something in Gaelic, which I did not understand. Mr Maclean interpreting for me, told me he said 'it was unlucky to disturb the bones of the dead!'..
..I am sorry to add, our labours at the cairn were not productive of much information. We dscovered nothing; but in casting out the stones I found several of that description of stones which are venerated in Mull for their imaginary virtues: also several specimens of beautiful black Mica.
Mr M. said, and I believe it with truth, that cairns were not erected merely where a person was interred, but often to commemorate the spot on which he died; and also at all the places where his body rested, from the place of his death to the place of his interment.
The old man informed us, he remembered the time when at any common funeral in Col, if the body was carried by that cairn, every one of the attendants cast a stone upon it. It is an expression of friendship and affection, at this hour among the islanders, to say, 'I will cast a stone upon your cairn!'
"We discovered nothing" yet he found axeheads? What was the man hoping for I wonder. From p235 of 'The Life and Remains of the Rev. Edward Daniel Clarke' (a professor of mineralogy at Cambridge) by William Otter (1824) - viewable on Google Books. The excavation took place in 1797.
Canmore says that "According to local tradition it was opened about 1765 by three Norwegians in the presence of the laird of Coll. They took the relics discovered home with them, claiming them to belong to a fellow-countryman." Well maybe that's why the Rev. was disappointed..