From an engraving on the title-page of Theophilus Jones’s History of the County of Brecknock, volume 2, 1809.
But I found it in ‘Long barrows of the Cotswolds’ by OGS Crawford (1925)
archive.org/details/in.ernet.dli.2015.283470/page/n79
Image credit: Richard Hoare / JM
