Two pieces of stoney folklore from the vicinity. I doubt they're connected to the rock art (they rarely are) but there various natural rocks and even a ruined chambered tomb in the Brahan Woods.
[..]Mr. W. Mackenzie, Procurator Fiscal of Cromarty, writes me from Dingwall (10th September, 1917) as follows:
"We are not without some traces and traditions of phallic worship here. There is a stone in the Brahan Wood which is said to be a 'knocking stone.' Barren women sat in close contact upon it for the purpose of becoming fertile. It serves the purpose of the mandrake in the East. I have seen the stone. It lies in the Brahan Wood about three miles from Dingwall."
'In close contact' - what a polite way of putting it.
And another, also fowarded by Sir James Frazer:
In the Brahan Wood there are a number of conglomerate boulders, some of considerable size. Two of these boulders lean against each other, meeting near the top. A few years ago an old woman aged 84 died near this town. When she was a child she had a fit - perhaps a convulsion - which her parents supposed to be epileptic. They lighted a fire at the top of the leaning stones, and passed the child through the opening below. This reminds one of the Biblical account of passing through the fire to Moloch."
W Mackenzie, Dingwall.
Women Fertilized by Stones
J. G. Frazer
Folklore, Vol. 29, No. 3. (Sep. 30, 1918), p. 254.
Scotch Cures for Epilepsy
Folklore, Vol. 29, No. 1. (Mar. 30, 1918), p. 86.