BORIS KARLOFF IN THE MUMMY. Elizabeth Taylor in Cleopatra. Whether inspired by such luminous Hollywood hieroglyphs or (according to Menil director Josef Helfenstein) by a book given to him by Marian B. Javits, wife of the New York senator, Robert Rauschenberg’s “Early Egyptians,” 1973–74, the series ending his cardboard-related works, all quietly glimmer in a gaudy twilight, due to Day-Glo pigment painted on their backsides in orange, yellow, pink, green, violet; situated near the edges of a room, as they were last spring in the Menil Collection’s “Robert Rauschenberg: Cardboards and Related