“At one end of the room is the batting cage, made of two nets, 20×80 feet, which are suspended from ropes stretched from wall to wall.” New York Herald, February 13, 1887, p7
“An innovation in methods of baseball practice is about to be introduced at the University of Chicago in the shape of an outdoor batting cage. The idea is [Amos Alonzo] Stagg’s own and has never been made use of before by any team.” The Chicago Tribune, March 19, 1896, p8
- NOTE: Many earlier mentions, like the 1887 one above, all refer to an indoor cage. The Stagg cage was not on wheels, but is the earliest I could find referring to an outdoor cage. (Ken Liss)
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1906. “[Oscar] Knolls lambasted Joe Tinker in the side in the batting cage today, and Joe has an ugly bruise” (Chicago Tribune, March 23; Peter Morris).