Ashmolean The Elements of Drawing, John Ruskin’s teaching collection at Oxford

I place next the most beautiful instance I ever saw of the use of horizontal lines by the Pisans, and of the ποικιλία of the inlaid marbles in association with the Gothic forms which they had derived from the North. This palace, on the South side of the Arno is, I suppose, of the early xiv.th Century, and especially delightful to me in the proportions of its shafts and arches, and E. in the treatment of its Decoration; with full trust in the spectator's careful watchfulness of the slightest variations, venturing all claim upon his admiration on the disposition of four flower-like stars, four crafts-of-arms and two crosses at the top. The lower drawing is an enlargement of one of the windows as seen from below. It ought to have been semi-circular; but I cannot draw from nature otherwise than as she sits (or stands) to me, and this was the real look of the window from the point, steeply beneath it where I stood. To make it quite right the Verticals should have been in retiring Perspective; but this would have been too offensive, and the error must, therefore, be pardoned.