Señor del Rescate. probably by Diego de Mora - early XVIII century.
Rublev's icon — also known as "Old Testament Trinity"— portrays a profound theological meaning of the unity of Persons in the Trinity along with the spiritual nature of God's Divine Essence by depicting the Triune God as simply three angels.
The 13th century Trinitarian mosaic by Lorenzo Cosmati on the northeast facade of the church of San Tommaso in Formis, on the Caelian Hill in Rome, Italy.
The Trisagion Rosary: Three sets of 9 beads gets you into Trinitarian contemplation.