"In Houstry, Dunbeath, Caithness, about the year 1809 or 1810, David Gunn, a crofter, in the course of making a kail-yaird, interfered with one of those prehistoric ruins known as Brochs which are so numerous in that northern region. Now it was well known that this Broch was a fairy habitation, and, in any case, it was well known that to tamper with a Broch or to carry away any of its materials was extremely uncanny."
But Mr Gunn didn't take any notice, and unfortunately a plague broke out that decimated the cattle of the whole district. Thanks a lot.
The was a meeting of local important types, and they decided on a Teine-Eigin as the best step forward. So they got a branch and stripped off its bark, and purified it by popping it on a little island in the Houstry Burn, so it was separated from everydayness by the flowing water. Everyone put out any fires that were burning. Then someone made a fire with the purified wood, and all the other fires were kindled from it anew.
The contributor of this story actually sent in a photo of one of these special bits of wood. It's got round dips in it as though it's been used (maybe) for making fire by a bow/drill method. But it hasn't got little v-shaped notches like wot Ray Mears would recommend.
R. C. Maclagan
Folklore, Vol. 9, No. 3. (Sep., 1898), pp. 280-281.