According to Z6Mag a 3 year old swallowed 37 BuckeyBall magnets. I had no idea what these were, so in case you are like me, here is a video link to the story from a TV station in Portland Oregon
The doctors were able to remove the magnets during an invasive surgical procedure. By the time Payton Bushnell had surgery, the magnets had already damaged her lower intestine and ripped a small hole in her stomach, but they were able to repair the tears and holes in surgery.
So I can see how a 3 year old would try to eat these. My wife would call these a major choke able. Don't think she would even let these in our house.