“Knox was perhaps the first to recognise the stone triangle. He records one from Ramsdale Hill Top, two miles west-south-west of Robin Hood’s Bay made of stones 4-6 feet high; also three small stones near a small barrow at Dry Heads, Harwod Dale. Another near Stoup Brow forms an acute triangle, the tallest stone known as the Grey Horse Stone being not more than 5 feet high”.
Frank Elgee
Early Man in N.E. Yorkshire
1930