Elemental mercury isn’t very bioavailable so licking the surface of a pool of mercury isn’t going to hurt you much if at all. (Assuming you just do it once). Plus the density of mercury is going make it hard for you to slurp up a significant quantity the stuff anyway.

If you want to know about the horrible potential for mercury to mess you up look for stories about dimethyl mercury exposure. Its the fat soluble varieties that give mercury it’s reputation.