This magical sounding spot is on the slopes of Beinn Lora above the cairn, less than half a mile away. So I thought you might like to hear about it. On the 1870s map it seems to be at NM 91892 37029.
It’s recorded in the Ordnance Survey Name Books for Argyll, collected 1868-78 (you can see the nice handwritten entry online at Scotlands Places.)
There’s Tobar Bial na Buaidh, the well of the virtuous water: “a small spring on the hill side to the north of Achnacreemore. It was much frequented in old times, even in the memory of some yet living, on account of the supposed virtues of its waters in curing disease.”
And Craobh Bial na Buaidh, the tree of the virtuous water: “a tree which stands near the above well. In the trunk of this tree there is a large hollow into which it was considered necessary for any person either drinking or taking away any of the water of the well to deposit something lest they should incur the displeasure of the spirit who was supposed to keep watch over it (the well).”