He [ndr : un peintre] must not only have a nice Judgment to distinguish betwixt things nearly Resembling one another, but not the same […], but he must moreover have the same Delicacy in his Eyes to judge of the Tincts of Colours which are of infinite Variety ; and to distinguish whether a Line be streight, or curv’d a little ; whether This is exactly parallel to That, or oblique, and in what degree ; how This curv’d Line differs from That, if it differs at all, of which he must also judge ; whether what he has drawn is of the same Magnitude with what he pretends to imitate, and the like ; and must have a Hand exact enough to form these in his Work, answerable to the Ideas he has taken of them.
RICHARDSON, Jonathan, An Essay on the Theory of Painting. By Mr. Richardson. The Second Edition, Enlarg'd, and Corrected, London, A. C. - A. Bettesworth, 1725.