 Also included were the beaver, due to its scaly tail and considerable time spent in water, and barnacle geese, due to the belief that they developed underwater in the form of barnacles.Such foods were also considered appropriate for fast days, though rather contrived classification of barnacle geese as fish was not universally accepted.The Holy Roman Emperor Frederick II examined barnacles and noted no evidence of any bird-like embryo in them, and the secretary of Leo of Rozmital wrote a very skeptical account of his reaction to being served barnacle goose at a fish-day dinner in 1456.