G. W. Eve, Heraldry as art: An account of its development and practice… (1907)
“ In the mediaeval period eagles were always shown on shields in the pattern-like displayed position, whether they were single or double headed, until Renaissance heraldry in its reversion to classic types introduced the eagle of the Roman Ensigns and Monuments, which thenceforth has had to be taken into account when eagles are described in blazon. Thus it is now necessary to state whether the bird is displayed, is close or is rising. An eagle is close when it stands in profile with its wings folded, and is rising when it stands in the same general position but with its wings raised. ”
