This cartoon caricatures him as both a conductor and composer. The picture includes what people heard as non-musical sounds: songbirds, roosters, bells, trains, howling dogs, and cannons. One man falls asleep in exhaustion. Others have collapsed after being struck by the instruments or the notes themselves.
Mahler's conducting style, 1901, caricatured in the humor magazine Fliegende Blätter
Here are my previous posts about sketching conductors: