It allegedly marks the place at which Marion Lillie, known as the Rigwoody or Ringwoodie Witch, was burnt in 1698, but the area around Spott was notorious for its witch burnings in the seventeenth and eighteenth centuries.
Indeed, East Lothian in general was infamous during this period, with towns such as Haddington, Tranent and North Berwick also being involved in some of the more well-publicised witch trials. Many commentaries claim that Lillie was the last witch to be burnt in Scotland, but this is clearly not the case, as can be seen from the Kirk Session Records, as quoted by Rev. John Martin in the late eighteenth century:
1698. The session, after a long examination of witnesses, refer the case of Marion Lillie, for imprecations and supposed witchcraft, to the presbytery, who refer her for trial to the civil magistrate. — Said Marion, generally called the Rigwoody Witch.
Oct. 1705. Many witches burnt on the top of Spott loan.
However, Lillie's association with this tone appears to be of more recent invention, since in 1836, we find the Rev. Robert Burns Thomson quoting the above passage and then continuing thus:
It is generally believed, that the last witch who was executed in Scotland was burnt at Spott; a stone commemorative of the event, and marking the place of execution, is to be seen a little way to the east of the manse.
From this, we can see both that the last witch was not Lillie, and thus the stone was not necessarily associated with her, or at least her alone. It should also be mentioned that almost every parish in the country has a legend about "the last witch burnt in Scotland" being a local!