Through its numerous reputed properties, rue early found its way into the magic cauldron.
'Then sprinkles she the juice of rue,
With nine drops of the midnight dew,
From lunary distilling,'
as Drayton has it. In this incantation, again, we have the association with moonwort; and the connection is further illustrated in an old oracle ascribed to Hecate: 'From a root of wild rue fashion and polish a statue; adorn it with household lizards; grind myrrh, gum, and frankincense with the same reptiles, and let the mixture stand in the air during the waning of a moon; then address your words.'
With regard to the association with moonwort, it is interesting to recall that this is one of the plants supposed to be employed by birds for opening nests and removing impediments. Thus in an anecdote gravely related to Aubrey, we find this virtue mentioned: 'Sir Bennet Hoskins told me that his keeper at his parke at Morehampton, in Herefordshire, did for experiment's sake drive an iron naile thwart the hole of a woodpecker's nest, there being a tradition that the dam will bring some leafe to open it. He layed at the bottom of the tree a cleane sheet, and before many houres passed, the naile came out, and he found a leafe lying by it on the sheete. They say the Moonwort will doe such things.'
On the same subject Coles, the botanist, writes: 'It is said, yea, and believed, that Moonwort will open the locks wherewith dwelling-houses are made fast, if it be put into the keyhole.' And Culpeper, the herbalist, writes thus: 'Moonwort is a herb which, they say, will open locks and unshoe such horses as tread upon it. This some laugh to scorn, and these no small fools neither; but country people that I know call it Unshoe-the-horse. Besides, I have heard commanders say that on White Down in Devonshire, near Tiverton, there were found thirty horseshoes pulled off from the feet of the Earl of Essex's horses, being there drawn up in a body, many of them being newly shod, and no reason known, which caused much admiration.' As well it might! This power of the moonwort is said to be still believed in in Normandy, and a similar virtue was also ascribed to the vervain and the mandrake, both associated with rue.
This curious property of moonwort it is which is referred to in Divine Weekes thus:
'Horses that, feeding on the grassy hills,
Tread upon moonwort with their hollow heels,
Though lately shod, at night go barefoot home,
Their maister musing where their shoes become.
Oh, moonwort! tell me where thou hid'st the smith,
Hammer and pinchers, thou unshodd'st them with?
Alas! what lock or iron engine is't
That can the subtle secret strength resist?
Still the best farrier cannot set a shoe
So sure but thou, so shortly, canst undo.'
The old alchemists, however, had a more profitable use for moonwort than the unshoeing of horses; they employed it for converting quicksilver into pure silver, at a time when that metal was neither 'degraded' nor 'depreciated.'
There is an old and pleasant belief, of which John Ruskin makes effective use in driving home one of his morals, that flowers always bloom best in the gardens of those who love them. One could easily find a rationalistic explanation of this sentiment, of course, but it is akin to a superstition entertained in some parts that wherever the moonwort flourishes the owner of the garden is honest.
The ingredients thrown into the mystic cauldron by European sorcerers were in close imitation of those of the ancient alchemists. Moncure Conway has pointed out that among the ingredients used by English and Scotch witches were plants gathered, as in Egypt, at certain seasons or phases of the moon. Chief among such plants were rue and vervain. The Druids called vervain the 'Holy herb,' and gathered it when the dog-star rose, placing a sacrifice of honey in the earth from which they removed it.