Sung as the clock strikes 5 a.m. by Magdalen choir on the summit of Wolsey's Tower (Oxford) on May morning to greet the rising sun. Some say the custom dates from the reign of Henry VIII.; if this overshoots the mark, no one knows for certainty a more exact period.
Te Deum Patrem collmus, Te laudibus prosequimur; Qui corpus ciboriflcis, Coelesti mentem gratia.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894