On the left is a drawing of the early Westbury white horse by Richard Gough which was published in the 1772 edition of Camden's Britannia. The printing plate was accidentally reversed, and in the book the horse is shown (incorrectly) facing right. On the right is an enlargement and ninety degree rotation of the horse as shown on a 1773 map. Below is a section of the map itself, and the horse can be seen to face left. The discovery of the map showing the horse facing left is described in The Lost Horse of Westbury, by D. Egdell, published in 3rd Stone magazine, Oct-Dec 1999.
Gough gives the horse's dimensions as "extreme length, 100 feet; extreme height, nearly as much;" and thus his drawing must be from below and so foreshortened, accounting for the difference in the horse's proportions in the drawing and on the map.