Stephenson:Neal:Quicksilver:552:Duc d'Arcachon (Neal Stephenson)

From the Quicksilver Metaweb.

This entire family (de Lavardac/d'Arcachon) is fictitious. People who are familiar with the history of France in the era of Louis XIV will, I hope, find this family and their exploits fairly plausible, and representative of a whole class of old-line hereditary nobles.