1845 reference to J T Smith's illustrated book, published in 1797, defining a compositional "Rule of Thirds":
"Sir Joshua Reynolds has given it as a rule, that the proportion of warm to cold colour in a picture should be as two to one, although he has frequently deviated therefrom; and Smith in his 'Remarks on Rural Scenery,' would extend a like rule to all the proportions of a painting, begging for it the term, "the rule of thirds," according to which a landscape, having one third of land, should have two thirds of water, and these together forming about one third of the picture, the remaining two-thirds to be for air and sky; he applies the same rule to the crossing of line, etc."
