The Trisagion Rosary
The Order of the Most Holy Trinity for the Redemption of Captives was founded in France by St. John de Matha and St. Felix of Valois in 1198. From the very early stages of the of order, the Trinitarians have used a form of prayer based on the Trisagion (sometimes Trisagium or Triagion, from the Greek “three” + ”holy”). This is a Byzantine prayer still used in the Divine Liturgy in the Eastern Orthodox, Oriental Orthodox and Eastern Catholic churches in praise of the Holy Trinity: its simplest form is “Holy God, Holy Mighty One, Holy Immortal One, have mercy on us.”
The Trisagion Rosary (also called a chaplet) has three sets of nine beads each. When reciting the Trisagion Rosary, each set begins with the Trisagion: “Holy God, Holy Mighty One, Holy Immortal One, have mercy on us.” ) and the Pater Noster. An invocation is said on each of the nine beads: “To you be praise, glory, and thanksgiving for ever, blessed Trinity. Holy, Holy, Holy, Lord God of power and might; heaven and earth are full of your glory.” Each set of nine prayers is followed by a Gloria Patri ("Glory be to the Father, and the Son, and the Holy Spirit..."), and the recitation of the rosary ends with a closing prayer.