Read "The Giza Power Plant, Technologies of Ancient Egypt" - Christopher Dunn
Not necessarily using mercury but there's evidence to suggest that Great Pyramid was an energy generator.
In more recent times, mercury was used in the plasma engines of antigravity craft. I think its usage has been replaced by other technology because mercury had the disadvantage of transmuting into gold, over time, reducing the efficiency of the engine and requiring a periodic cleanout.
Read "The Giza Power Plant, Technologies of Ancient Egypt" - Christopher Dunn
Not necessarily using mercury but there's evidence to suggest that Great Pyramid was an energy generator.
In more recent times, mercury was used in the plasma engines of antigravity craft. I think its usage has been replaced by other technology because mercury had the disadvantage of transmuting into gold, over time, reducing the efficiency of the engine and requiring a periodic cleanout.