⁴Loomis, Laura H. A. "Geoffrey of Monmouth and Stonehenge." PMLA 45.2 (1930): 400.
According to Loomis, this story was first printed in 1724 and repeated in an 1821 publication. E. H. Wood (1924) thinks that it may have originated from a tale told to the author of the 1724 book, John Wood.