I imagined the road to unraveling a 500-year-old Leonardo da Vinci mystery would take me down rain-slicked flagstones in the crepuscular shadow of a glowering Tuscan cathedral, or perhaps through the mote-strewn catacombs of a Florentine palazzo. Instead, my first stop is a prim brick colonial on a broad, verdant thoroughfare in suburban St. Paul, Minnesota. I pull into the driveway and come to a stop in front of a tin-can robot standing astride the porch.
“My mother made it for me,” explains Mark Rosheim, a roboticist who has produced designs for NASA and Lockheed Martin. His living room is dominated by two hulking cabinets, each filled with oversize editions of da Vinci codices. It is, the owner suggests with the slightest bravado, “the largest collection of Vinciana in the Midwest.” He points to one set, a dozen volumes of the Codex Atlanticus, the thousand-page collection of drawings that is da Vinci’s best-known work. “I got that one from Christie’s in London through a telephone bid,” he says. “That was before eBay. The auction was at 4 in the morning. It was very exciting.”
On one wall, there is a family picture frame with a series of oval and square photos. “This is the whole Mark Rosheim saga,” he says. His father’s drugstore. His computer science-trained brother. His grandfather, a pioneering dentist who owned the first x-ray machine in Story City, Iowa. And Rosheim at a Cub Scout gathering at age 9. He is dressed as a robot.
As we tour the house, I get the feelin...