“Before 1814, when it was destroyed by a farmer, the Odin Stone, a holed stone at Croft Odin, Orkney, was used for oath-taking. In 1791, a young man was arraigned by the Elders of Orkney for ‘breaking the promise of Odin’, that is, breaking an oath sworn on the stone. When visiting the stone ceremonially, it was customary to leave an offering of a stone or a piece of bread, cheese or cloth.”
From “Celtic Sacred Landscapes” by Nigel Pennick 1996, page 53.