This document provides an overview of the historical liturgy of the catechumens. It describes the transitional ritual that began with readings to introduce pagans to Church doctrine and included preparatory prayers by the priest. It also outlines the opening parts of the liturgy, including litanies, hymns, and the Trisagion. Additionally, it details the initial incensing ritual performed by the deacon after the proskomidia to sanctify the church with incense while Psalm 50 is recited silently.