The 1978 facsimile reprint of Henri Boudet’s La Vraie langue celtique contained a preface by Pierre Plantard, published by Éditions Belfond (les classiques de l’occultisme).

In his preface to this edition, Plantard invented the fantasy that Abbé Henri Boudet provided Abbé Bérenger Saunière with a total of 13 million francs between 1887 and 1915, paid via Marie Dénarnaud.

The notability of the book lies in Plantard’s Bibliography, revealing which works inspired him in his Priory of Sion mythmaking process.