Traditionally, Christians are not supposed to eat meat on Fridays, but fish is acceptable. However, the temptation often proved too great to resist, and a number of loopholes were developed to get around the rule. Perhaps the most unusual of these was the belief that barnacle geese spontaneously generated from driftwood. Since this made them not proper birds, they could be eaten on Fridays. At the Fourth Council of the Lateran in 1215, Pope Innocent III had to explicitly forbid eating barnacle geese on Fridays, saying that whatever their origin, they lived and ate like other birds, and so were to be considered birds.