Rex Sempiterne Caelitum (5th century)
The pre-Urbanite version—called “Rex Sempiterne Domine”—is so radically different from the 1631AD revision that the Brébeuf Hymnal provides a completely different translation on pages 418-419.
In addition to providing the Latin version with accent marks, the Saint Jean de Brébeuf Hymnal commissioned English translations from Latin scholars to help congregations appreciate these ancient prayers. Until the Brébeuf Hymnal appeared in 2018, literal translations for many of these hymns had never been made.