From the 2004 edition of the Roman Martyrology for the 8th of November:
Commemoratio sanctorum Simproniani, Claudii, Nicostrati, Castorii et Simplicii, martyrum, qui, ut traditur, fabri marmorarii apud Sirmium in Pannonia, cum simulacrum dei Æsculapii propter nomen Iesu Christi fingere renuissent, a Diocletiano imperatore in fluvium præcipites dari jussi sunt et a Deo martyrii gratia coronati; quorum Romæ sub titulo Quattuor Coronatorum in basilica Cælimontana veneratio ab antiquitus floruit.(The commemoration of SS Simpronianus, Claudius, Nicostratus, Castorius and Simplicius, martyrs, who, as has been handed down, were sculptors in marble near Sirmium in Pannonia [now Sremska Mitrovitsa in Serbia]; when they refused to make an idol of the god Æsculapius on account of the name of Jesus Christ, by the Emperor Diocletian they were commanded to be taken and thrown into the river [Sava] and by God were crowned with the grace of martyrdom; whose veneration at Rome under the title of the Four* Crowned ones in the basilica on the Cælian hill has flourished from of old time.)
[* There was some confusion even in the earliest ages as to their exact names and number; in recent centuries their true history has been uncovered and vindicated against the jibes of Holy Church's enemies, who made much of the cult given to saints whose very names were at one time lost and unknown - forgetting what St Paul had said (Acts xvii, 23) about the wisdom of those Athenians who had reared an altar "To the Unknown God", and thus unwittingly served the cause of Truth.]
According to the Index of the Martyrology, they were martyred in 306. Here is their proper Collect, taken from their commemoration to-day at Lauds:
Præsta, quæsumus, omnipotens Deus: ut, qui gloriosos Martyres fortes in sua confessione cognovimus, pios apud te in nostra intercessione sentiamus. Per...(Grant, we beseech, almighty God, that we, who have known the glorious Martyrs strong in their confession, may feel their pious intercession with thee in our behalf. Through...)
Woe to Diocletian! He is mentioned on well nigh every page of the Martyrology - but he is not a saint. Mors peccatorum pessima: The death of sinners is the worst.
- St Clarus, priest at Tours, disciple of St Martin (c. 396);
- Pope St Deusdedit I (618);
- St Willehad, first bishop of Bremen, a friend of Alcuin, an Anglo-Saxon from Northumbria who came to the Continent to preach the Gospel in the footsteps of St Boniface to the Frisians and Saxons (789);
- St Geoffrey (Godefridus), bishop of Amiens (1115);
- Bl John Duns Scotus, the Subtle Doctor, far-famed Franciscan friar and professor at Canterbury, Oxford, Paris and latterly Cologne where he died in 1308;
- Bl Mary Crucified, Abbess (1745);
- The holy Vietnamese Martyrs SS Joseph Nguyen Dinh Nghi, Paul Nguyen Ngan, Martin Ta Duc Thinh (priests), alongside Martin Tho and John Baptist Con, farmers, who were beheaded in Tonkin for the Faith of Christ under Emperor Thieu Tri in 1840.
Look at this list! Bishops and sculptors, priests, friars and farmers, even an abbess: in every age God is pleased to raise up friends worthy of Himself; pray that He may number us among them (Æterna fac cum Sanctis tuis in gloria numerari).
As we would go on to pray at Prime, after the Martyrology is read:
And elsewhere many other holy Martyrs and Confessors, and also holy Virgins. Thanks be to God.Precious in the sight of the Lord: is the death of His Saints.May Holy Mary and all the Saints intercede for us with the Lord, that we may deserve to be aided and saved by Him, Who liveth and reigneth evermore. Amen.
This portion of prayer from the Anglican tradition - which with the Book of Divine Worship is licitly given its true home in the Roman fold - is I think very apposite to add as well:
And we yield unto thee most high praise and hearty thanks, for the wonderful grace and virtue declared in all thy Saints, who have been the choice vessels of thy grace, and the lights of the world in their several generations: and chiefly in the blessed Virgin Mary, Mother of thy Son Jesus Christ our Lord and God, and in the Holy Patriarchs, Prophets, Apostles, and Martyrs, beseeching thee to give us grace to follow the example of their stedfastness in thy faith, and obedience to thy holy commandments, that at the day of the general resurrection, we, and all they who are of the mystical body of thy Son, may be set on his right hand, and hear his most joyful voice, Come ye blessed of my Father, inherit the kingdom prepared for you from the foundation of the world. Grant this, O Father, for Jesus Christ’s sake, our only Mediator and Advocate. Amen.