"I'm going to put my baby in a cage outside the window of my apartment so that s/he can get some fresh air." Saying that out loud in the world we currently live in would end with you having your children taken away from you, and you would likely end up behind bars yourself.
In the early 1900s, the practice of "airing" your baby was quite popular in major metropolitan areas like New York City. New York is a city of apartments, and for any of you who have ever lived in a stuffy little apartment with children, you can understand why parents were willing to try this. Fresh air was considered a pinnacle point of having a healthy child, so why not hang them out a window high above the streets?
Emma Read applied for a patent on a "portable baby cage" in 1922. Some people, including Eleanor Roosevelt, were improvising with their own homemade versions of these contraptions, but they weren't considered "safe". Roosevelt's was actually a chicken wire cage that she would just hang out the window of her New York home. Neighbors were mortified and threatened to call the police.