E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Crape . Lawn.
A saint in crape is twice a saint in lawn. (Pope: Ep. to Cobham, 136.) Crape (a sort of bombazine, or alpaca) is the stuff of which cheap clerical gowns used to be made, and here means one of the lower clergy; lawn refers to the lawn sleeves of a bishop, and here means a prelate. A good curate is all very well, but the same goodness in a bishop is exalted as something noteworthy.