The Quaternion Eagle[needs IPA] (German: Quaternionenadler; Italian: aquila quaternione), also known as the Imperial Quaternion Eagle (German: Quaternionen-Reichsadler)[1][2] or simply Imperial Eagle (German: Reichsadler),[a] was an informal coat of arms of the Holy Roman Empire.
Introduced around 1510 by Hans Burgkmair, the Quaternion Eagle mixed two pre-existing concepts: the Imperial Quaternions and the Imperial Eagle (double-headed eagle).[a]
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