The ceremony of holding the stirrup of an arriving high-status guest, illustrated here showing Emperor Frederick Barbarossa doing it for Pope Adrian, kneeling beside the horse and holding the stirrup as the pope mounts. This kind of thing casually for any arriving minor noble from anywhere was a brilliant way for Medici to perform non-princliness, since it's usually a servant's job (hence the pope humiliating the emperor by making him do it) but look at those harshly bent knees!
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