Magnalia naturæ: or, The truth of the philosophers-stone asserted [electronic resource] : having been lately expos'd to publick sight and sale. Being a true and exact account of the manner how Wenceslaus Seilerus the late famous projection-maker, at the Emperours Court, at Vienna came by, and made away with a very great quantity of pouder of projection, by projecting with it before the Emperor, and a thousand vvitnesses, selling it, &c. for some years past. Published at the request, and for the satisfaction of several curious and ingenious, especially of Mr. Boyl, &c. By one who was not only a ey-witness in the affair, but also concern'd as a commissioner by the Emperor for the examen of it.