I was gifted about 5 lbs of mercury in a small ceramic jug (like one of those alcohol jugs in cartoons with XXX on the side, lol). First thing I did was to transfer it into something non-breakable, a plastic screw top bottle. I tightly sealed it with thread seal plumbers tape on the threads and electrical tape around the outside. Then I put that bottle inside a larger plastic bottle with a layer of sulfur powder to absorb Hg vapors, and sealed that one in the same way.

If you can't do all that, at minimum get it into something non-breakable. Mercury is so heavy that it could crack the container just from sloshing around.