He collaborated in the publication of the Roman Catechism, presided over the Commissions for the reform of Roman Breviary and Roman Missal, and directed the work of the new edition of the Roman Martyrology.
He published more than 30 books and over 75 pamphlets including prayer books, Bible stories for children, lives of the saints, and catechisms.
There is some conjecture that he was a martyr in Rome, a conjecture that entered earlier editions of the Breviary.
It was notable for publishing Ad Completorium which contained the complete text and music for Compline according to the Roman Catholic Breviary of 1961.
No. 7 is assigned in the Roman Breviary to Monday at Lauds, from the Octave of the Epiphany to the first Sunday in Lent and from the Octave of Pentecost to Advent.
In April 2012, its much anticipated Latin-English Roman Breviary was published, having been granted an imprimatur by Bishop Fabian Bruskewitz.
The Breviary Hymns of the Rosary were the four hymns that were sung during the Liturgy of the Hours for the Feast of the Rosary.
The Aberdeen Breviary, compiled by the King's "traist counsalar" Bishop William Elphinstone of Aberdeen, is apparently an example of this policy.
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The Breviary was compiled by Bishop William Elphinstone of Aberdeen and aimed to give the rituals of the Scottish Church a character distinctive from that in England and its dependencies.
The legend, told in the breviary of Lescar, printed in 1541, portrays Galactorius fighting the Visigoths at Mimizan at the head of an armed band and seeking help from Clovis.
In 2007 he arranged for the publication of replica volumes of William Playfair's Atlas as well as his Statistical Breviary, the first books on the subject.
According to Janet Backhouse, former head of manuscripts at the British Library, “the Isabella Breviary is one of the most valuable treasures in the British Library’s enormous manuscript collection, a work the reflects both the artistic and the political history of its period (…) this acquisition is one of the most important purchases of an illuminated manuscript in the history of the British Museum and its library.”1
In 1888 Legg faced the public with the first fruits of a series of editions he was to produce in the next three decades: an edition with Cambridge University Press of the reformed breviary devised and published by Cardinal Quiñones in 1535.
In 1484–1494 in Grobnik he copied the Drugi novljanski brevijar ("The Second Novi Vinodolski Breviary") for the Pauline monastery in Novi Vinodolski, a Glagolitic codex in 500 folios.
The work received the name of Banister's Breviary of the Eyes in which the curative properties of Malvern water are also mentioned.
, a sermon in which he criticises the rise of the early Baptist churches in England such as those lead by Thomas Lambe; An Historical Vindication of the Government of the Church of Scotland; The Life of William (Laud) now Lord Archbishop of Canterbury Examined (London, 1643); A Parallel of the Liturgy with the Mass Book, the Breviary, the Ceremonial and other Romish Rituals (London, 1661).
He was one of the compilers of the Roman Catechism and a member of the commission charged by Clement VIII with the revision of the Breviary.