I observe, that of late Chymistry begins, as indeed it deserves, to be cultivated by Learned Men who before despis’d it; and to be pretended to by ma… - Robert Boyle

Those distinct substances, which concretes generally either afford, or are made up of, may, without very much inconvenience, be called the elements or principles of them.

But I will not... trouble you with what I have largely discoursed in the Sceptical Chymist, to call in question the grounds on which Chymists assert, that all mixt bodies are compounded of Salt, Sulphur, and Mercury. For it may suffice me now to tell you that, whatsoever they may be able to obtain from other bodies, it does not appear by Experience, which is the grand, if not the onely, Argument they rely on, that all mixt bodies that have Qualities consist of their tria prima, since they have not been able, that we know, truly, and without new Compositions, to resolve into those three, either Gold, or Silver, or Crystal, or Venetian Talck, or some other bodies, that I elsewhere name; & yet these bodies are endowed with divers Qualities, as the two former with Fusibleness and Malleability, and all of them with Weight and Fixity; so that in these and the like bodies, whence Chymisats have not made it yet appear, that their Salt, Sulphur and Mercury, can be truly and adequately separated, 'twill scarce be other than precarious to derive the malleableness, colour, and other Qualities of such bodies from those Principles.

I consider, that as generally as Chymists are wont to appeal to Experience, and as confidently as they use to instance the several substances separated by the Fire from a Mixt Body, as a sufficient proof of their being its component Elements: Yet those differing Substances are many of them farr enough from Elementary simplicity, and may be yet look'd upon as mixt Bodies, most of them also retaining, somewhat... of the Nature of those Concretes whence they were forc'd.