Sure, but if you have a sufficient amount of mercury, that amalgam will remain invisible to the eye as Mercury is not translucent - and you can just write "mercury" on the flash and you can be sure no-one will dare to touch it.
When I was at school (1980s) the teacher had us line up and put our fingers in a flask of mercury. It was a very peculiar sensation. I probably wouldn't want to repeat that "experiment" today.
Sure, I'm not saying the general knowledge of mercury poisoning was commonplace back then, but in the scientific community it was, I believe, well known already.
Mercury poisoning has been known for some time, however people in the general public knowing or caring about mercury poisoning is a pretty recent phenomenon.
Sure, but if you have a sufficient amount of mercury, that amalgam will remain invisible to the eye as Mercury is not translucent - and you can just write "mercury" on the flash and you can be sure no-one will dare to touch it.