From Dom Guéranger's The Liturgical Year.
As we return from Palestrina to the Eternal City, we pass on our left the cemetery of Saints Marcellinus and Peter, where were first deposited the holy relics of the pious empress Helena, who entered heaven on this day. The Roman Church deemed no greater honour could be given her than to mingle, so to say, her memory on May 3 with that of the sacred Wood which she restored to our adoring love. We shall not, then, speak to-day about the glorious discovery, which, after three centuries of struggle, gave so happy a consecration to the era of triumph. Nevertheless, let us offer our homage to her who set up the standard of salvation, and placed the Cross on the brow of princes who were once its persecutors.
Prayer
Domine Jesu Christe, qui locum, ubi crux tua latebat, beatæ Helenæ revelasti, ut per eam Ecclesiam tuam hoc pretioso thesauro ditares: ejus nobis intercessione concede; ut vitalis ligni pretio æternæ vitæ præmia consequamur. Qui vivis.
O Lord Jesus Christ, who unto blessed Helena didst reveal the place where Thy Cross lay hid: thus choosing her as the means to enrich Thy Church with that precious treasure: do Thou, at her intercession, grant that by the price of the Tree of Life we may attain unto the rewards of everlasting life. Who livest and reignest, etc.