The eagle has always been considered the most powerful and majestic bird in the sky, due to the height of its flight and, according to Aristotle, its ability to take off facing the sun. Present in Egyptian, Hittite, Sumerian and Babylonian cultures, the Grecians associated it with the Divinity, representing it accompanied by Zeus-Jupiter, and with rays trapped in its talons. The Roman legions carried it on their banners from 104 B.C., later Charlemagne adopted the eagle as the symbol of the Roman Empire; in the emblem the eagle was black on a golden background, it was also the symbol of the Roman "Res Publica". In Germanic mythology it was associated with Odin. In the Middle Ages it was depicted in a very stylised form on coats of arms and heraldic emblems, looking to the right (in heraldry, a view to the right is a symbol of legitimacy). It has frequently been placed on the top of buildings, on columns and on obelisks as a symbol of majesty, of empire, or alluding to its capabilities. Never has an icon such as the eagle been so aptly represented as an emblem of imperial majesty and power, and like all symbols it also has a dark aspect, the perversion of this power, a predatory and cruel bird, with the capacity to oppress and dominate all that is inferior to it. In Christian iconography, as a bird that kills snakes, it summarises the victory of light over the powers of darkness. In the Tetramorphous the eagle corresponds to Saint John the Evangelist, and in the Bible, it is the emblem of the Omnipotence of God and the power of faith, also representing Christians, who, baptised in Christ, have died, and risen with Him. Among the deadly sins it represents pride. In alchemy its meaning does not substantially change the above, and it is the symbol of sublimation. An eagle devouring a lion symbolises the triumph of the spirit and the volatilisation of matter. The two-headed eagle is attributed a Mesopotamian origin, its oldest representation is found on a seal from Lagash, III millennium B.C., where under its claws it has two lions. From Hittite art it reached the West, by the hand of Byzantium, where it was associated with the Roman deity Janus. During the Crusades it reached Eastern Europe, where the Russian Empire took it as its emblem, but it was King Frederick II who established it as the symbol of the Empire in the West, and by analogy of the two-headed lion in the Austro-Hungarian Empire. In philosophical symbolism, it is usually represented with two tones, white and red, or black and white, colours of great symbolic significance that represent the dualism of creation.