Among the prerogatives of every emperor who received the command by divine will, the relationship with the positive symbolic values of the eagle has always been at the forefront: among these the ability to see beyond, to be enlightened, in some ways a clear-clairvoyant, qualities attributed in fact to the bird of prey. In the Bestiary by Philippe de Thaon (pp. 2013 and following) of 1126 there are these verses about the eagle: «Egle est rei de oisel, / mult mustre essample bel. / En latine raisun / “clear-veant apellum”, / kar le solail verat / quant il plus cler serat, / tant dreit le esguarderat / ja le oil ne cillerat, ecc» (The eagle is the king of the birds; it shows a very beautiful example. In Latin it is rightly called “clear-clairvoyant”, because it looks at the sun when it is brighter and although it looks fixedly at it, never turns away, etc.).
The Latin Physiologist (Versio Bls, VIII), which according to some thinkers dates back to the time of Charlemagne, reports about the fanciful etymology attributed to the word eagle by Isidoro “Aquila ab acumine oculorum vocata” (The eagle is so called because of the acuteness of its eyes): “It has such an acute sight that when it planes on the sea with its immovable wings, invisible to human eyes (nec humanis pateat obtutibus), from so great a height it is able of to perceive small fishes that swim, then, going down rapidly, it grabs its prey and with a flap of it’s wing it drags it up to the shore. It is said that it doesn’t turn from the rays of the sun and that it even puts its brood through that proof, suspended to its claws: those that are able to look fixedly at the sun, are judged worthy to belong to the stock of eagles and it holds on to them but he  lets the ones that look elsewhere fall, as degenerate ones”. Here the symbolism of the eagle is compared to the ability of the emperor to see beyond, to his faculty of perceiving “from afar” the things that are necessary to his kingdom (therefore to his children) and as well as his ability to choose, to determine what to maintain and what to eradicate for the good of his people.
The eagle appears in the Visconti Sforza Tarot deck of Yale on the headgear of the Emperor who holds the usual signs of the command in his hands, the sphere and the sceptre (figure 1), while in the production of most of the subsequent tarots it is engraved on the imperial shield.
With regards to the eagle, an upward symbol, a sign of exclusive high power and to the other symbolic values attributed to people in command, see what has been written in reference to the eagle in the Empress card.
In the Tarots of Charles VI deck the sitting Emperor has two pageboys at his side and holds the sceptre that culminates in a lily and the golden globe (figura 2). The baton of command, present in numerous narrations of the Old Testament, was used in ancient times by all dignitaries of high rank. The globe, for its spherical shape that connects it to the symbol of the circle and therefore of infinity, is often represented in the hands of God (figure 3 - Albrecht Dürer, The Seventh Day of the Creation, woodcutting from Liber Chronicarum, 1493) or of Christ to be subsequently attributed to all the Sovereigns on earth (figure 4 - Michael Wohlgemut, Cambise, woodcutting from Liber Chronicarum, 1494).
The presence of the lily in the Charles VI card, doesn’t mean that a French emperor was represented, since this flower was largely adopted in the European heraldry, even if its origin dates back to the so-called Lily of France.
Its heraldic meaning in fact appears in various natures. The flower, for its colour, represents purity innocence of mind, honesty and consequently rectitude, and on the other hand it can represent acceptance of the divine wish, that is Providence that provides for the needs of its chosen ones, as we find in the biblical tradition in Matthew (6, 28): “Observe as the lilies of the field grow;  they don’t work and they don’t spin, yet abandoned in the hands of God, the lily is decorated better than Solomon in all his glory.” In the Charles VI card - as in any other representation linked to characters of power where the lily is present - the flower represented the particular properties of the sovereign that, as we have seen, consisted of purity and honesty of the aims towards which he governed, as well as showing that people would never be abandoned to themselves, but continually helped by the emperor who would provide for their needs in the problematic moments of their existence.
In the card in the Mantegna Tarots deck (figure 5) and in the one in which Emperor Theodosius is represented together with Pope Paul II (Constitutions of the Bolognese study, cod. ms. 40, Bologna, Public Archives), borrowed from the same card, the figure of the Imperator has crossed feet. It doesn’t deal with a particularly usual attitude, but appears as an external mark of safety and of correct evaluation, adopted by judges as they are passing sentence, as we find in the Sachsenspiegel in Dresden (figure 6), which Van Rijnberk amply examined (Tarot. Histoire, Iconography, Esoterism, 1947, pp.108-113).
After the XVI century the image of the Emperor in  tarots did not change substantially; iconography conformed with the attributes of the sceptre,  the globe and the shield with the eagle on it. In some cases, as in the Vieville Tarot deck, the globe is positioned on top of the sceptre, on which there is a cross (figure 7). The cross, the  double joining of diametrically opposite points, represents the symbol of the unity of  extremes - for instance the sky and the earth -, of synthesis and measure. In it, time and space are united and because of this, even before Christ, it became the most universal symbol of mediation, of the mediator. In this case the emperor's  prerogative to be mediator between God and men concerning  temporal power.  
In the Wirth Tarots deck the Emperor sits on a cubic throne, on which the figure of an eagle appears (figure 8). Many thrones had such a structure on their bases since “the volume of a square in a square has the same significance as the surface of a square; it represents the material world and that of the four elements together and, for its solid equilibrium, it has been assumed to be a symbol of stability” (Jean Chevalier-Alain Gheerbrant, Dictionary of Symbols, 1986, page.358). According to Wirth the cubic throne is the only one that cannot be upset because its stability derives from the geometric shape attributed by the Alchemists to the Philosophical Stone.