The Greatest Minor League: A History of the Pacific Coast League, 1903-1957, by Dennis Snelling (McFarland, 2011), Kindle Loc. 834-843:

The defensive play of 1911, or indeed any other year, was made by twenty-eight-year-old Vernon Tigers center fielder Walter Carlisle, whose name should be synonymous with the term “circus catch.” One of the fastest players in the league, he was known for his peculiar method of diving for fly balls. After making the catch, he rolled into a forward somersault before popping back to his feet to execute the return throw to the infield.

Carlisle’s unmatched feat occurred in the sixth inning of a July 19 game between the Tigers and Angels. With the scored tied, 3-3, and Angels base runners George Metzger and Charlie Moore at first and second with no one out, Tigers manager Happy Hogan brought Harry Stewart in to relieve starting pitcher Alex “Soldier” Carson.

The Angels’ next batter, Roy Akin, hit a low line drive just beyond the reach of the infielders. Certain the ball would drop, Metzger and Moore took off immediately. Playing in center field, Carlisle had positioned himself extremely shallow, directly behind second base, and got a terrific jump. At the last moment he dove, snagging the ball before it touched the ground and tumbling into a double somersault. Neither Angels base runner realized Carlisle had made the catch. When he popped back to his feet, Carlisle saw that Moore had already rounded third, so he ran in and touched second base for another out. Realizing the other runner, Metzger, had passed second base and could be easily beaten back to first, Carlisle calmly trotted over to complete what remains the only unassisted triple play by an outfielder in the history of professional baseball.