The WebMD page is about calomel, mercuric chloride, and perchloride of mercury, not metallic mercury; the body text is clear about this, but the title is wrong. It describes all kinds of poisoning symptoms that don't occur with metallic mercury. So too for the mercury section of the Science Museum web page, except for a brief mention of attempts to treat with mercury vapors. And neither of them seems very credible.
My source did not note that people tried liquid mercury.
“Mercury has been employed in one or other of its forms in almost all diseases”
Are you really saying that in that time, no one tried the most obvious form?
You’re right though that I was wrong it was the primary one - I’m truly horrified at the various things people tried. But I guess untreated syphilis is one of the worst possible ways to die, and I’d try pretty much anything too.
My source did not note that people tried liquid mercury.