Here is the description of the Mass from the letter of Justin Martyr above. It is from 150 AD. The portions in brackets are mine, and generally relate the modern portion of the Mass to what is being described.
Justin Martyr
Selections from Apologia (c. 150 AD)
And on the day called the Day of the Sun [Sunday] there is a gathering in one place of us all who live in cities or in the country [The Mass], and the memoirs of the Apostles or the writings of the prophets are read as long as time allows [The Liturgy of the Word]. Then, when the reader has ceased, the priest gives by word of mouth his admonition and exhortation to imitate these excellent things [The Homily]. Afterward we all rise at once and offer prayers; and as I said, when we have ceased to pray, bread is brought and wine and water, and the priest likewise offers up prayers and thanksgivings as he has the ability, and the people assent, saying “Amen.” [The Presentation of the Gifts] The distribution to each and the partaking of that for which thanks were given then take place; and to those not present a portion is sent by the hands of the deacons. Those who are well-to-do and willing give, every one giving what he will, according to his own judgment, and the collection is deposited with the priest, and he assists orphans and widows, and those who through sickness or any other cause are in want, and those who are in bonds, and the strangers that are sojourning, and, in short, he has the care of all that are in need [The Offertory Collection]. Now we all hold our common meeting on the Day of the Sun, because it is the first day on which God, having changed the darkness and matter, created the world; and Jesus Christ our Savior on the same day rose from the dead. For on the day before Saturn’s they crucified Him *; and on the day after Saturn’s; which is the Day of the Sun, having appeared to his Apostles and disciples, He taught them these things which we have offered you for consideration…
…But after we have thus washed him who is persuaded and has assented [here discussing a newly baptized person], we bring him to those who are called the brethren, to where they are gathered together, making earnest prayer in common for ourselves and for him who is enlightened, and for all others everywhere, that we may be accounted worthy, after we have learned the truth, by our works also to be found right livers and keepers of the commandments, that we may be saved with the eternal salvation. [The General Intercessions / Prayers of the Faithful] We salute each other with a kiss when we conclude our prayers [The “kiss” is the Sign of Peace]. Thereupon to the priest of the brethren bread and a cup of water and wine are brought, and he takes it and offers up praise and glory to the Father of the universe through the name of the Son and the Holy Spirit, and gives thanks at length that we have been accounted worthy of these things from Him; and when he has ended the prayers and thanksgiving the whole people present assent, saying “Amen.” [The Eucharistic Prayers / The Consecration] Now the word Amen in the Hebrew language signifies, So be it. Then after the priest has given thanks and all the people have assented, those who are called by us deacons give to each one of those present to partake of the bread and of the wine and water for which thanks have been given, and for those not present they take away a portion. [Communion]
And this food is called by us Eucharist, and it is not lawful for any man to partake of it but him who believes the things taught by us to be true [Communion is open only to Catholics and considered a sacrament of initiation], and has been washed with the washing which is for the remission of sins and unto a new birth, and is so living as Christ commanded [Communion may not be partaken in by the unbaptized]. For not as common bread and common drink do we receive these; but just as Jesus Christ our Savior, being made flesh through the word of God, had for our salvation both flesh and blood, so, also, we are taught that the food for which thanks are given by the word of prayer which is from Him, and from which by conversion our flesh and blood are nourished, is the flesh and blood of that Jesus who was made flesh [the Real Presence]. For the Apostles in the memoirs composed by them, which are called Gospels, thus delivered what was commanded them: that Jesus took bread and gave thanks and said, This do in remembrance of Me, this is My body; and that He likewise took the cup, and when He had given thanks, said, This is My blood [Mt 26:17-19; Mk 14:12-16; Lk 22:7-13], and gave only to them…*
