“The Unknown Masterpiece” was written more than a hundred years ago, but it continues to exert a fascination for tortured painters and perfectionists of all kinds. It haunted Cézanne, who identified with Balzac’s tragic hero, and it was illustrated, somewhat carelessly, by Picasso. It is still assigned by teachers and read by painters, as an emblem of the madness of the search for absolute perfection. It’s a little hard to believe Frenhofer (how could he fail to see his beloved figure was invisible?), but he is a wonderful epitome of hopeless obsession.