What is the fine-grained topic of the following text: The following spring, Wagner (who in 1903 led the league in batting average) refused to send his portrait to a "Hall of Fame" for batting champions.Due to overflow crowds at the Exposition Park games in Allegheny City, if a batted ball rolled under a rope in the outfield that held spectators back, a "ground-rule triple" would be scored. Only return the topic.
Historical incidents in baseball featuring Wagner and the Exposition Park games.