James Boswell's uncle John was a member of a sect known as the Glasites.
Jean Louis L'Estocq
Referred to by Boswell only as "L'estocq", Boswell on the Grand Tour I, 1763-1764 identifies him as Jean Louis L'Estocq.
According to Boswell, he was formerly (i.e. before September 1764) tutor to the princes of Anhalt-Dessau, probably Albrecht, and Johann George and possibly even to the then reigning Prince Leopold III.
Life with Boswell:
Boswell had some conversation with L'Estocq at the Court of Dessau on September 26, 1764.