I heard that the first emperor of China slept on a feather mattress in a pool of mercury to prevent assassination. I wonder what that weighed? Unfortunately for him he also ingested it regularly in an attempt to become immortal. It didn’t work.
The Lewis and Clark expedition carried mercury in their supplies. It was administered by Capt. Lewis to some of the men who contracted the clap from dallying with the natives.
WEll; I've slept on a feather mattress. It was really light weight IIRC.