
Mercurius in the Air Famae alchymine, Leipzig 1717
The most characteristic chemical trait of mercury is association. It links itself up in the most unexpected ways. The tendency to form complex compounds is very marked in the case of mercury.(2) It combines with nitrogen and carbon compounds which metals normally won't touch, as well as forming the usual metal salts, and forms complicated 'organometallic' mercury compounds, which catalyse the synthesis of a range of pharmaceutical and other organic, man-made products. It forms explosives (e.g. mercury iodide) which detonate at a mere touch. In amalgamating other metals together, it performs this interlinking function.
The Indian word for alchemy was Rassayana which means the way of mercury. The earliest alchemical texts in the West date from the first century AD, and this is also when the first texts for obtaining mercury from its ore cinnabar appear. Pliny the Roman naturalist gave such a recipe. Heating of the red ore cinnabar causes it to sweat globules of the shining metal; then, careful heating the mercury again yield a red ore (although this is the oxide, no longer the sulphide). This was the classic recipe whereby alchemists impressed their clients, and was the first inkling of a chemical reaction. Mercurys changeable nature seemed to manifest mysteries of matter. Hermes in his Egyptian form as thrice-greatest was the patron of alchemy, in which mercury had the central role. Alchemists who reckoned they could make gold would usually start off with mercury (which is, as chance would have it, next to gold in the Periodic table)

Mercurius in water
The orbit of this fastest-moving of planets was an enigma for a century. The plane of Mercury's orbit kept 'precessing' or shifting about in a way that defied explanation, and Newtons theory could not account for it. Mercury resisted this materialistic world conception, and it was only explained in the 20th century by the Theory of Relativity. Likewise, the metal mercury resists the solid state. It is the secret, the mystery of quicksilver, that a metal of such enormous density can yet remain liquid. It is not difficult to see why the alchemists credited mercury with a very special inner mobility and vitality.
Ancient Indian texts tell of Vimana which were fabulous flying craft (e.g. in the Mahabarata). These texts inform us that the craft were powered by mercury. Clearly, speedy mercury was just the stuff to power these mythic ancient craft! The commonest daily use for mercury sees it in constant motion - the thermometer. Hermes was traditionally the god of medicine, and Mercury was for long given an important role in medical practice. It was for centuries the staple remedy for syphilis, and even today it is still used for skin ointments-calomel-and the sublimate is used as a disinfectant. Mercury amalgams are used in dentistry, and mercurial aids such as the thermometer and blood pressure apparatus aid the doctor. Thus the different aspects of the Mercury-nature are expressed both by the metal and by the planet in the sly, in accordance with the Hermetic maxim, 'as above, so below.'
Mercury is always on the move, and nowadays it is coming out from circulation: from batteries, from tooth fillings, from gold amalgamation processes, etc, so that Euro- experts have a problem what to do with it. Thousands of tonnes of it might be placed carefully down one or two of the mines whence it was obtained! As Mercury is removed from large-scale use, we may be sure that other subtle properties of this mysterious and elusive element will turn up in due course.
References
1)Newton, 'Optics' 1717, Query 30
2) J.R.Partington, 'A Textbook of Inorganic Chemistry' 1960 p.795.