The visitor was the Comte Louis Philippe de Ségur, and the excerpt originally hails from "Memoires ou 8ouvenirs et Anecdotes", Vol. 2. S. 126 ff. (Paris 1827).(Volz is good with his footnotes.) Ségur was a French diplomat and writer, on his way to become the French envoy at Catherine's court and making a stop in Berlin to meet Europe's most famous fan of French literature.