arcanist

noun2

1. •
   A person who studies arcana or religious mysteries.

   • There were on this Occasion not far from us some of the Clergy, […] and also Arcanists or Dealers in Mysteries — 1791
2. •
   (historical) A craftsman who has knowledge of a manufacturing secret (specifically in the area of porcelain manufacturing).

   • The porcelain manufactory likewise entertains, excepting the modellers and arcanists, none but russian workmen […] — 1799