Mercury, along with sulphur and salt are one of the three essentials that get mentioned over and over. Mercury, above all, deserves it’s own page. A related concept is “Philosophical Mercury”. Sometimes confused with the philosopher’s stone, but not the same thing. Isaac Newton commented on this, saying that getting to the philosophical mercury is the first step on the right track, but not the same thing.
Only metal to be liquid at room temperature. In the ancient theory of elements it was said to be the essence of air and water.
Innermost planet, named after the Roman God.
“cold” and “dry”
In Roman mythology he’s the messenger of the gods. The equivalent is Hermes and Thoth, and is therefore the very roots of Western alchemy.