Few people have ever visited Oak Spring Farms, the grand home here of Rachel Lambert Mellon, better known as Bunny. If they had, they would have seen a Pissarro, unframed like a flea market find, above the living room fireplace. Upstairs, a still life by van Gogh hung above her bathtub. Antique porcelains — cabbages, asparagus, artichokes — were artfully arranged on practically every surface.

Mrs. Mellon was the matriarch of an American dynasty whose fortune and art holdings rivaled that of the Fricks, Carnegies and Morgans. But perhaps most notably, she was a passionate collector of a bygone era. She didn’t pay attention to what was in fashion; she didn’t think about future financial returns.