In the April, 2005 issue of National Geographic Magazine on SpaceShip One (couldn't anyone have come up with a more imaginative name for this ship?), I learned one interesting item:

Brian's job wasn't going to be easy. To qualify SpaceShipOne for the ten-million-dollar Ansari X Prize, he had to fly himself and the equivalent of two passengers—a total of 595 pounds (270 kilograms)—to an altitude of at least 100 kilometers (328,000 feet) and return for a safe landing. We'd measured his payload precisely. But nobody had planned on Brian's mother-in-law contributing a last-minute surprise. As Brian got ready to enter the cockpit, she gave him a big hug, spilling a cup of coffee all over his flight suit.

"I got soaked," Brian said. "I later figured those extra 12 ounces probably cost me 200 feet of apogee."

http://www7.nationalgeographic.com/ngm/0504/feature3/