In the 10th century Book of Ceremonies (Bk. 1, Ch. 17) by Emperor Constantine Porphyrogennetos we read that on the feast of Mid-Pentecost, which landed on a Wednesday, the Emperor would lead a procession from his palace in Constantinople to the Church of Saint Mokios. There we have a reference to a church dedicated to Saint Onesimos, which the procession would pass when they entered the Exokionion district, and when they arrived at this church, they turned right and passed the Church of Saint James the Persian. This is the earliest reference to a church in Constantinople dedicated to this disciple of the Apostle Paul and slave of Philemon, who is commemorated in the Synaxarion of Constantinople on February 15th.