I learned this from About.com's account of the incident, which includes this:
The golfer was Carl Cooper, who at the time was a 31-year-old journeyman. The tournament was the 1992 Texas Open, played that year at Oak Hills Country Club in San Antonio. ...
... On the par-4, 456-yard third hole, Cooper launched his drive ... On the fly, the ball hit a downward-running concrete cart path and took off.
The ball rolled past the fifth green. Then it passed the sixth tee. It eventually left the cart path and veered onto an unpaved maintenance road. And finally it came to a stop behind the No. 12 green.
According to the story, Cooper's caddie measured it at 787 yards from the third tee. Read the rest of the story here.