A quick search suggests either heating it, or nitric acid. I can imagine either working. Heating it means you’re boiling off the mercury, of course, and should be done with good ventilation. Nitric acid dissolves mercury, but won’t dissolve gold.
The dangers of mercury are not overstated, but they are misunderstood IMO. Hg(0) (that is the liquid metal that we are discussing here) is not very toxic at all. Rolling it around in your hand and being amazed at the way it behaves is not likely to cause any harm. Unfortunately, like most metals, mercury oxidizes on exposure to air. In fact, it does this quite quickly in part because it is a liquid. When mercury oxidizes it becomes Hg(II), which is very toxic. Someone said that mercury sulphate wasn’t toxic and that may be comparatively true, but if you get it in your lungs or someplace wet where it can slowly exchange ions all bets are off.
This is why all the hysteria about mercury. If you are playing with it in your hands, it is quite difficult to control. You are likely to drop some, and it will break up and roll into the cracks where it can slowly evaporate for your body to absorb. This may not even cause noticeable damage, but it may. The fact is that mercury exposure is usually unnecessary. Since it is a cummulative poison, it would be irrational not to do everything possible to eliminate potential exposure. That means no longer letting school childeren roll it around in their hands. Nevertheless, some exposure is inevitable. I’m not terribly worried about eating salmon. The dental amalgams have been shown to be safe, though for the price I’ll avoid them.
As for pennies that have been amalgamized and recirculated, I think this is bad. Unlike with the dental amalgam, this amalgam has not been created under controlled conditions. There is no reason to believe that the crude mercury copper amalgam has the same stability as the dental amalgams.
As for how it feels, I have nothing new to add. I’ve handled several jars of it and it feel like liquid lead. I’ve broken several thermometers and mercury bubblers and the cleanup was a hassle. I have quite deliberately never touched it directly. The scariest mercury experience I’ve had was carrying the doubly sealed and never opened bottle of diphenyl mercury accross the room. That is a scary mercury compound.