There is a tremendous patience in Henri Rousseau (b. 1844), on view as part of a major exhibition at the Barnes Foundation in Philadelphia. His Rendezvous in the Forest (1889) meticulously reproduces dense woodland foliage, a constellation of leaves blanketing the surface of the canvas and nearly concealing the illicit couple at its center. This is the work of an artist who knew how to bide his time, an artist whose primary profession was waiting—Rousseau served as a customs agent at a toll gate in Paris for over two decades, the source of his nickname, Le Douanier Rousseau. Yet Rousseau’s work is hardly observational—a reminder that staring at the same view every day may mean we see less, rather than more, of it. Instead, he pursued an imaginative practice often characterized as “naïve,” though “Henri Rousseau: A Painter’s Secrets” dispels such illusions. The show is a collaboration between the Barnes and the Musée de l’Orangerie in Paris, and includes work from the collection of the Parisian dealer Paul Guillaume. Guillaume sold Albert Barnes many of …