The feather's best documented single use is in the Weighing of the Heart, the judgment scene set out in the Book of the Dead and painted in numerous tomb and papyrus contexts, in which the deceased's heart, understood in Egyptian belief as the seat of conscience and moral record rather than the brain, is placed on one pan of a scale against the Feather of Ma'at on the other. Assmann's reading treats the scene as the logical endpoint of Ma'at as a lived ethical standard rather than only a court doctrine: a heart burdened by wrongdoing outweighs the feather, and the outcome recorded across surviving versions is the deceased's destruction or denial of continued existence, consumed by the devouring figure Ammit who waits beside the scale, while a heart balanced against the feather passes into the afterlife.
The scene makes Ma'at, otherwise an abstract organizing principle of Egyptian religion, into a concrete, individually applied test at the moment of judgment. Ammit, the composite devouring figure waiting beside the scale in surviving Book of the Dead illustrations, combines the forequarters of a crocodile, the body of a leopard or lion and the hindquarters of a hippopotamus, a specific and consistent iconographic combination across numerous copies of the text, underlining how standardized this particular judgment scene became once it was established rather than varying freely between versions.