Some of them evidently took it to mean the substance then, and now, called mercury; the results of this literal interpretation were disastrous; others thought of mercury as a substance which could be obtained, or, at any rate, might be obtained, by repeatedly distilling ordinary mercury, both alone and when mixed with other substances; others used the word to mean a hypothetical something which was liquid but did not wet things, limpid yet capable of becoming solid, volatile yet able to prevent the volatilisation of other things, and white, yet ready to cause other white things to change their colour; they thought of this something, this soul of mercury, as having properties without itself being tangible, as at once a substance and not a substance, at once a bodily spirit and a spiritual body.
It was impossible to express the alchemical ideas in any language save that of far-fetched allegory.

The alchemical writings abound in such allegories.

Here are two of them.
The first allegory is taken from _The Twelve Keys_, of Basilius Valentinus, the Benedictine:-- "The eleventh key to the knowledge of the augmentation of our Stone I will put before you in the form of a parable.
"There lived in the East a gilded knight, named Orpheus, who was possessed of immense wealth, and had everything that heart can wish.

He had taken to wife his own sister, Euridice, who did not, however, bear him any children.

This he regarded as the punishment of his sin in having wedded his own sister, and was instant in prayer to God both by day and by night, that the curse might be taken from him.