magistery

A pure quality with the power to cure or to turn one substance into another; also, a substance such as a philosopher's stone able to turn one substance into another.

[T]hey made proofe of the ſaid flowers dried, and this high magiſterie they found, That being beaten to pouder, they cured thoſe of the bloudie flix,^([sic – meaning flux]) vvho lay at the very point of death upon that diſeaſe; […]

[…] I have been here long enough, if I were matter capable thereof, to be made the Philoſophers Stone, to be converted from VVater to Povvder, vvhich is the vvhole Magiſtery: I have been beſides, ſo long upon the Anvil, that methinks I am grovvn malleable, and hammer-proof: I am ſo habituated to hardſhip.

The product of such a transformation.

A fine substance deposited by precipitation, formerly applied to certain white precipitates from metallic solutions.

magistery of bismuth (BiONO₃·H₂O)

I am apt to think, that either Simples, or cheap, or unelaborate Galenical Mixtures, may furnih us vvith Specificks, that may perform much more than Chymiſts are vvont to think, and poſſibly be preferable to many of their coſtly Magiſteries, Quint-eſſences and Elixirs. […] The more Judicious of the Chymiſts themſelves do ſeveral of them novv acknovvledge, that the bare reducing of Pearls to fine Povvder, affords a Medicine much richer in the Vertues of the Pearls, then the Magiſtery, prepar'd by diſſolving them in acid Spirits, and precipitating them vvith Oyl of Tartar, and aftervvards ſcrupulously edulcorating them.

A concentrated extract of a substance.

An art or a skill.