I was watching this clip from the 2017 film The Mummy in which the characters stand next to a pool of mercury which was being used as part of an elaborate prison.
Several comments under this video imagine that standing next to a pool of mercury would be very dangerous, but I can't see any reason to think that a significant amount of vapour would be coming from the pool so it seems like the mercury just being there in liquid form would be quite harmless. But maybe I shouldn't go robbing any graves any time soon.
The automatic warning dialogue told me the question appears quite subjective. So, let's say you're standing next to the pool for no more than ten minutes and we'll define harm as requiring medical intervention or (if chronic) as having a demonstrable, long-term health effect, such as erethism. I have no idea how large the pool is in the video, but for the purposes of the question, we'll say it's a circular pool of 10 metres in diameter.