'Hitherto Undescribed Cup- and Ring- Marked Stones.' Fred R Coles. Proc Soc Antiq Scot 37 (1902-03)
On page 228 and 229 is a description of the "Witches' Stone" at Tormain Hill. I have added a copy of the diagram. The stone has 22 cupmarks in a dog-legged line across 9ft of stone, and a 23rd at a distance just where the kink in the line is. More about it on p143+ of volume 10 (1872-4).
Tiompan tells me this stone is sadly no longer with us, having been willfully destroyed by some philistine (see forums). It's said to have been used in 'fertility rituals' with young ladies* sliding down it.
*i.e. the Witches! and their shocking behaviour.
Having used the word 'dog-legged' I synchronicitously found Charles Fort reporting that the holes are said to be 'the tracks of dogs' feet' (maybe that's why – they don't really look like tracks of a four-footed animal). His 'Book of the Damned' cites the Proc Soc Antiq Scot "2-4-79" but I have not read the original.