The preparation of Phosphorus

Phosphorus was first recorded as being made by Hennig Brandt in 1669, but although he was willing to show this to others, Brandt was unwilling to pass on the exact formula. In the 1670's, Kunckel, Kirchmaier and Boyle also experimented with phosphorus. Georg Kaspar Kirchmaier, Noctiluca constans et per vices fulgurans..., Wittenberg, 1676. Johann Kunckel Oeffentliche Zuschrifft von dem phosphoro mirabili..., Leipzig, 1678. Robert Boyle, The aerial noctiluca: or some new phoenomena, and a process of a factitious self-shining substance. London, 1680. Around 1685, Boyle's assistant, Hanckiewicz, set up a factory to manufacture phosphorus.

The account of its preparation below is taken from William Y-Worth, Chymicus Rationalis... In which is contained, A Philosophical Description of the Astrum Lunare Microcosmicum, or Phospheros. London, 1692. [It is rather amusing to ponder over what exactly motivated the researcher to make the final experiment in this series!]
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Now follows the Preparation of the Fosperus, or the Astrum lunare Microcosmicum.

As is before shewed, take Urine well putrefied in a Tub, exposed to the Air for seven Weeks, all one as you do when you're to make a Spirit of it; the Spirit being drawn, or rather the whole of it being evaporated to the consistance of Honey, in which lies the Fosperus; but the Art is somewhat difficult to get it from thence, in two cases, the one is in making choice of a proper Agent to be mixed therewith, and the other is the exact regiment of the Fire.
Now as to the Agent, it must not (as some have said) be Sand; but one that is free from Salt, and consequently from the glass-making Faculty, or any thing that will vitrifie, for if it doth that, you shall never obtain the Fosperus; but that you may, we direct you to make use of a Fire within and without your Vessel, which is thus to be understood; take the Sap of Urine, as before 'tis said, or that of Dung and Urine putrified together, and incorporate it with Charcoal-dust, and put it into a German Retort, and lute on a Receiver, that is filled half full with Water, that when the Fosperus comes over, it may immediately drop into the Water and be preserved thereby.
Observe, That you are to begin with a very small Fire, but you are to increase it gradually into the highest degree that possibly can be made, and let it be in such a Furnace, that upon occasion the Bellows may be used, and that the Fire may play well about the Vessel, continuing so long at its greatest heighth, till no more comes over, and you'l see Flakes like Lightening, that will come over in the Receiver of two substances, the one like a thick muddy Water, which will sink to the bottom, the other swimming over it; separate by inclination these two substances, and keep each by it self in a Glass, the gummy Nature may be made into what form you please, by being dissolved in Spirit of Sal Armoniack or other Urinous Spirits; in B. 'tis thereby putrified.

Observations concerning it.

It must always be kept in Water, for the Air sets it on fire.
The thick Liquor, if rubbed upon the Hands, Cloaths, or Hair, they will appear in the dark, as if all in fire, but will not burn, and if you open the Cork of the Glass, all its vacancy will appear like the flame of Brimstone.
If you put this thick Liquor, hardened by digestion into a Gum in Oyl of Cloves or of Cinnamon, and let it remain there 24 hours, and pour off the Oyl from it into a Glass, the same Oyl will as you pull out the Cork, and set it in the Air, appear so bright, that in the dark, if it's in a large and clear Viol, you may see it to read distinctly.
If you write upon the Palm of your Hand, or upon Paper with the said Gum, what ever you write will appear all on fire, and the Letters may be read a long time after; but you must have a great care, that you do it softly, and to put it into Water, as soon as you have done, for if it happen to fire 'twill burn the place most dreadfully.
Cut a little piece of the said Gum, and lay it upon Paper, and rub it on with the point of a Knife, and 'twill set the Paper on fire.
Put a little piece of the said Gum to steep 24 hours in Spirit of Wine, then taking it out again, if you pour this Spirit of Wine by drops upon a Bason of Water, you will see Flashes like Lightening, somewhat like the flame of Brimstone, and somewhat of a purplish colour.
Rx. Of the aforesaid Gum one drachm, and in a white earthen Vessel expose it to the Air, and the Air will set it on fire, and when it hath done burning, you will have four drachms of Spirit of Salt, which it attracts out of the Air.
If the Privy Parts be therewith rubb'd, they will be inflamed and burning for a good while after.