Today marks the 800th anniversary of the opening of the Fourth Lateran Council. Opened by Pope Innocent III on November 11th 1215 it closed on the following November 30th and was, of course, one of the most significant of General Councils of the Catholic Church.
Pope Innocent III
The best known contemporary image of the Pope.
I have seen it suggested that his pallium is conciously depicted in an archaic manner, and that in fact he would have worn it as it is today.
Lateran IV in session by Matthew Paris
Whether it fulfilled his hopes may be open to discussion but it certainly defined the Church as it was to be in the High and Late Middle ages. In the sixteenth century it was the point of reference for much of the debate between critics and defenders of what was then the established order.
There is an online introduction to the Fourth Lateran Council at Fourth Council of the Lateran
The Council's profession of faith is here:
Chapter I. The Catholic Faith
Firmly we believe and we confess simply that the true God is one alone, eternal, immense, and unchangeable, incomprehensible, omnipotent and ineffable, Father and Son and Holy Spirit: indeed three Persons but one essence, substance, or nature entirely simple. The Father from no one, the Son from the Father only, and the Holy Spirit equally from both; without beginning, always, and without end; the Father generating, the Son being born, and the Holy Spirit proceeding; consubstantial and coequal and omnipotent and coeternal; one beginning of all, creator of all visible and invisible things, of the spiritual and of he corporal; who by His own omnipotent power at once from the beginning of time created each creature from nothing, spiritual, and corporal, namely, angelic and mundane, and finally the human, constituted as it were, alike of the spirit and the body. For the devil and other demons were created by God good in nature, but they themselves through themselves have become wicked. But man sinned at the suggestion of the devil. This Holy Trinity according to common essence Undivided, and according to personal properties distinct, granted the doctrine of salvation to the human race, first through Moses and the holy prophets and his other servants according to the most methodical disposition of the time.
And finally the only begotten Son of God, Jesus Christ, incarnate by the whole Trinity in common, conceived of Mary ever Virgin with the Holy Spirit cooperating, made true man, formed of a rational soul and human flesh, one Person in two natures, clearly pointed out the way of life. And although He according to divinity is immortal and impassible, the very same according to humanity was made passible and mortal, who, for the salvation of the human race, having suffered on the wood of the Cross and died, descended into hell, arose from the dead and Ascended into heaven. But He descended in soul, and He arose in the flesh, and He ascended equally in both, to come at the end of time, to judge the living and the dead, and to render to each according to his works, to the wicked as well as to the elect, all of whom will rise with their bodies which they now bear, that they may receive according to their works, whether these works have been good or evil, the latter everlasting punishment with the devil, and the former everlasting glory with Christ.
One indeed is the universal Church of the faithful, outside which no one at all is saved , in which the priest himself is the sacrifice, Jesus Christ, whose body and blood are truly contained in the sacrament of the altar under the species of bread and wine; the bread (changed) into His body by the divine power of transubstantiation, and the wine into the blood, so that to accomplish the mystery of unity we ourselves receive from His (nature) what He Himself received from ours. And surely no one can accomplish this sacrament except a priest who has been rightly ordained according to the keys of the Church which Jesus Christ Himself conceded to the Apostles and to their successors. But the sacrament of baptism (which at the invocation of God and the indivisible Trinity, namely, of the Father and of the Son and of the Holy Spirit, is solemnized in water) rightly conferred by anyone in the form of the Church is useful unto salvation for little ones and for adults. And if, after the reception of baptism anyone shall have lapsed into sin, through true penance he can always be restored. Moreover, not only virgins and the continent but also married persons pleasing to God through right faith and good work merit to arrive at a blessed eternity.
All the Canons can be read in translation or summary on the Fordham Medieval Sourcebook pages at Lateran IV - Internet History Sourcebooks Project
Pope Innocent III
The other surviving contemporary portrait. A mosaic in the Basilica of St John Lateran,
and which depicts the pallium as worn in succeeding centuries.