There are some helpful comments under the previous post about the historicity of the weekly Eucharist. The Didache has been brought forward, as well as the testimony of St. Justin Martyr. Both clearly state that the weekly Sunday gathering of Christians incorporated the Sacrament of Christ's Body and Blood.
But I'd like to go back even further. The Acts of the Apostles tells us that the Apostles celebrated the Eucharist daily.
"And day by day, attending the temple together and breaking bread in their homes, they partook of food with glad and generous hearts." (Acts 2:46)Even so, one can find evidence for the communal Sunday Eucharist in Acts 20:7,
"On the first day of the week, when we were gathered together to break bread, Paul talked with them."Here, "breaking bread" is not "have lunch together" but is a liturgical, communal event. It takes place on the "first day of the week", i.e. Sunday.