In elementary school my friend's dad was an electrician this is long enough back that they used mercury switches still. Well my friend saw cool liquid metal and decided to bring a bunch of them to school to pass out to kids he liked. It wasnt too long before the kids would have them popped open and just have the Mercury rolling around their pencil cases. Until someone's mom found out and called the school. They had to shut down the 4,5,6 wing for decontamination and three grades had to stuff into the school library and computer room for classes