James Boswell's uncle John was a member of a sect known as the Glasites.
Gerhard Christiaan Rücker
Professor of law at Utrecht University (around 1760).
Possibly the Johann Gerhard Christian Rücker (1722-1780) who was sometime professor at Groningen.1
Life with Boswell:
Boswell went to Rücker's lecture on September 20, 1763, before settling on following Professor Trotz's lectures instead.