White suits and butterfly nets

How did this image come to represent corraling the insane?

Harvey

Oh, it goes back long before that–it was already a well-known image by 1944, when the play was written.

Well, for one thing, most hospital workers did wear “white suits.” The “butterfly net” image goes at least back to the 1910s, probaby further. Becuase that’s what you’d use to catch something or someone that was fluttering around madly.

What I want to know is when did the “giant Napolean hat with a backwards N on it” begin?