Source, in full
Quoted in "A portion of the journal kept by Thomas Raikes, esq., from 1831 to 1847; comprising reminiscences of social and political life in London and Paris during that period.", volume 2. London: Longman, Brown, Green, Longmans and Roberts, 1858.
Notes from Wikiquote
Also attributed to Victor-François, 2nd duc de Broglie