According to Pope Boniface VIII's bull Unam sanctam (1302),
Indeed, at the time of the flood there was one ark of Noah, prefiguring the one Church, made complete in one cubit [Una nempe fuit diluvii tempore arca Noe, unam Ecclesiam praefigurans, quae in uno cubito consummata] (Denzinger-Hünermann 870)
What does it mean that the arc was "made complete in one cubit"?