Quite some time ago, I was studying some of the practices of the ancient apostolic church and ran across some of the writings of Justin Martyr. In his Apology 1.67, he describes just a portion of what took place in ancient times:
. . . and on the day called Sunday, all who live in cities or in the country gather together to one place, and the memoirs of the apostles or the writings of the prophets are read, as long as time permits; then, when the reader has ceased, the president verbally instructs, and exhorts to the imitation of these good things. . .