Found on the Am Baile website, from the John O’Groats Journal Christmas Edition 1929...
” The legend concerning it is that a month old son (which is English for Mac Mese) carried it there from the top of Ravens Rock, one of the surrounding hills. ”
ambaile.org.uk/en/item/item_page.jsp?item_id=92804
(click to enlarge photo, then look to bottom right corner)