Notices from contemporary narrative sources regarding the Diet of Augsburg held in January 1209.
MCCVIIII. Otto rex in epyphania celebrem curiam Augustae habuit, multis principibus praesentibus, tam ex Longobardia quam de aliis provinciis vel partibus convenientibus. Eodem quoque anno expeditionem in Italiam movit, Romamque veniens imperialem a domino papa Innocentio accepit benedictionem.
Post hoc apud castrum Noricum colloquium habens, a Bawaria in Alamanniam pervenit, ibique [rex Otto IV] in epiphania Domini apud Augustam colloquium habens, Ottonem palatinum de Witilinspach necnon markionem de Anadehse lege Bawarica sententialiter propter occisum Philippum proscripsit, eosque dignitatibus, beneficiis ac prediorum suorum redditibus sine spe recuperationis iudicialiter privavit, dignitates eorum in alios transferens, aliisque beneficia concedens, redditibus prediorum heredibus eorum delegatis, captisque ibidem quinque pacis violatoribus uno decollato quatuor suspensis.
During the Diet of Augsburg held in January of 1209 the patriarch of Aquileia Wolfger managed to procure three favourable charters for the Church of Aquileia: the first two were issued already in January 1209 during the Diet of Augsburg and they confirmed the possesions of the Aquileian chapter in Friuli (see the edition of the charter here) and the patriarchs' temporal lordship over the Duchy of Friuli (see the charter edition here); the third pertained to the Margraviate of Istria which was bestowed upon the Patriarchate of Aquileia during the Diet of Augsburg, but the official donation charter was issued in May 1210, after the formal annointment of Otto IV as the Emperor of the Holy Roman Empire in Rome (see the edition of the charter here).
The notices given by Otto IV's contemporaries - Conrad of Scheyern and Otto of St. Blasien - attest to an official imperial diet being held in Augsburg in 1209, but they fail to mention the confirmations and donation bestowed upon Patriarch Wolfger. Moreover, Otto of St. Blasien wrote as if "markio de Anadehse" (that is Istrian margrave Henry of House Andechs-Merania) was sentenced and deprived of his fiefs by King Otto IV during the Diet of Augburg, but this is not so; as read from Otto IV's charter from 1210 (see it here), the Istrian margrave was sentenced for the crime of lèse majesté already on the Diet of Frankfurt held in November of 1208.