E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
To measure other peoples corn by ones own bushel. To make oneself the standard of right and wrong; to appraise everything as it accords or disagrees with ones own habits of thought and preconceived opinions; to be extremely bigoted and self-opiniated.
Under a bushel. Secretly; in order to hide it.
Do men light a candle and put it under a bushel?Matt. v. 15.