In a French vegetarian cookbook with an inscription from its author, Maa Charpentier, I encountered Monsieur Hitler vgtarien. And I found hints of Hitler the future mass murderer in a 1932 technical treatise on chemical warfare that explores the varying qualities of poison gas, from chlorine to prussic acid (Blausure). The latter was produced commercially as Zyklon B, which would be notorious for its use in the Nazi extermination camps.