In appearance Frederick was a man of well-proportioned, medium stature, with flowing yellow hair and a reddish beard. He delighted in hunting and the reading of history, was zealous in his attention to public business, and his private life was unimpeachable. Carlyle's tribute to him is interesting: "No king so furnished out with apparatus and arena, with personal faculty to rule and scene to do it in, has appeared elsewhere. A magnificent, magnanimous man; holding the reins of the world, not quite in the imaginary sense; scourging anarchy down, and urging noble effort up, really on a grand scale. A terror to evil-doers and a praise to well-doers in this world, probably beyond what was ever seen since." The principal contemporary authority for the earlier part of the reign of Frederick is the _Gesta Friderici imperatoris_, mainly the work of Otto, bishop of Freising. This is continued from 1156 to 1160 by Rahewin, a canon of Freising, and from 1160 to 1170 by an anonymous author. The various annals and chronicles of the period, among which may be mentioned the _Chronica regia Coloniensis_ and the _Annales Magdeburgenses_, are also important. Other authorities for the different periods in Frederick's reign are Tageno of Passau, _Descriptio expeditionis asiaticae Friderici I._; Burchard, _Historia Friderici imperatoris magni_; Godfrey of Viterbo, _Carmen de gestis Friderici I._, which are all found in the _Monumenta Germaniae historica. Scriptores_ (Hanover and Berlin, 1826-1892); Otto Morena of Lodi, _Historia rerum Laudensium_, continued by his son, Acerbus, also in the _Monumenta_; Ansbert, _Historia de expeditione Friderici, 1187-1196_, published in the _Fontes rerum Austriacarum. Scriptores_ (Vienna, 1855 fol.). Many valuable documents are found in the _Monumenta Germaniae selecta_, Band iv., edited by M. Doeberl (Munich, 1889-1890). The best modern authorities are J. Jastrow, _Deutsche Geschichte im Zeitalter der Hohenstaufen_ (Berlin, 1893); W. von Giesebrecht, _Geschichte der deutschen Kaiserzeit_, Band iv. (Brunswick, 1877); H. von Buenau, _Leben und Thaten Friedrichs I._ (Leipzig, 1872); H. Prutz, _Kaiser Friedrich I._ (Dantzig, 1871-1874); C. Peters, _Die Wahl Kaiser Friedrichs I._ in the _Forschungen zur deutschen Geschichte_, Band xx. (Goettingen, 1862-1886); W. Gundlach, _Barbarossalieder_ (Innsbruck, 1899). For a complete bibliography see Dahlmann-Waitz, _Quellenkunde der deutschen Geschichte_ (Goettingen, 1894), and U. Chevalier, _Repertoire des sources historiques du moyen age_, tome iii. (Paris, 1904).