Frankly, that is ridiculous. Mercury is a rare element found on earth, and to find not only a lake of it, but a pure form that could be used has a "poison lake" in a tomb would have been next to impossible. Even with the high levels of mercury detected in the area, its very doubtful it is high enough to indicate a "lake". The amount of mercury required for such an endeavor would have been ludicrous as well.

The reason they don't excavate it further is because they worry about damaging the already fragile remains.

Try researching better in the future.

Thank u.... Thats right....