Recipe
1. Take good English Vitriol [sulfuric acid], dissolve it in warm water, using no more water than will dissolve it, leaving some of the imperfect part at the bottom undissolved.
2. Pour it off and filter it, which you may do so by a Coffin of fine gray paper put into a Funnel, or by laying a sheet of gray paper in a sieve, and pouring your water or Dissolution of Vitriol into it by degrees, setting the sieve upon a large pan to receive the filtered Liquor.
3. When all your Liquor is filtered, boil it in an earthen Vessel glazed, till you see a thin scum upon it.
4. Set the scum in a Cellar to cool, covering it loosely, so that nothing may fall in.
5. After two or three days standing, pour off the Liquor, and you will find at the bottom and on the sides large and fair green Christals [Crystals] like Emerauds [sic].
6. Drain off all the water clean from them, and dry them. Then spread them abroad, in a large flat earthen dish, and expose them to the hot sun in the Dog-days [hottest and most sultry days of summer, usually early July to early September], taking them in at Night, and setting them out in the Morning, securing them from the Rain.
7. When the Sun has calcined them to whiteness, beat them to Powder, and set this Powder again in the Sun, stirring it sometimes, and when you see it perfectly white, powder it, and sift it finely, and set it again in the Sun for a day.
8. You will have a pure white Powder, which is the Powder of Sympathy.
How to preserve
9. Put it up in a Glass, and stop it close [seal it]. The next year when the Dog days come, and if you still have any of this Powder left, you may expose it again in the Sun, spreading it abroad to renew its Virtue by the influence of the Sunbeams.
How to Use – the Way of Curing Wounds
10. Take some of the Blood upon a Rag, and put some of the Powder upon the Blood.
11. Then keep only the Wound clean, with a clean Linnen [sic] about it, and in a moderate Temper betwixt hot and cold, and wrap up the Rag with the Blood, and keep it either in your Pocket or in a Box, and the Would will be healed without any Ointment or Plaster, and without any pain.
*But if the would is somewhat old, and hot, and inflamed, you must put some of this Powder into a Porringer [a shallow bowl you eat porridge from] or Basin full of cold Water, and then put anything into it that has been upon the wound, and has some of the Blood or Matter upon it, and it will presently take away all Pain and Inflammation.
** To staunch the Blood either of a Wound or Bleeding at the Nose, take only some of the Blood upon a Rag, and put some powder upon it, or take a Basin with fresh water, and put some of the Powder into it, and bathe the Nostrils with it.
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also a helpful link: http://jonathantierney.blogspot.com/2010/07/powder-of-sympathy.html