The Didache is said to be one of the earliest non canonical christian writings. Like PeacefulPete mentioned, it doesn't give the traditional view of the eucharist. Here's a relevant portion of it:
Now about the thanksgiving, give thanks this way:
First, about the cup: "We thank you, our Father, for the holy vine of your boy David which you made known to us through your boy Jesus. Glory be to you for the age.
Now about the broken loaf: "We thank you, our Father, for the life and the knowledge that you made known to us through your boy Jesus. Glory be to you for the age. Just as this broken loaf was scattered on top of the hills and as it was gathered together and became one, in the same way let your assembly be gathered together from the remotest parts of the land into your kingdom. "For yours is the glory and the power through Anointed Jesus for the age." Now no one should either eat or drink from your thanksgiving meal, but those who have been baptized into the Lord's name. For about this also the Lord said, "Do not give what is holy to the dogs."
Now after you have been filled, give thanks this way: "We thank you, holy Father, for your holy name, which you made to live in our hearts, and for the knowledge and trust and immortality which you made known to us through Jesus your boy. Glory be to you for the age.
"Almighty master, it was you who created all for the sake of your name. You gave both food and drink to people for enjoyment, so that they might give thanks to you. But to us you have freely given spiritual food and drink and eternal life through your boy. Before all things, we are thankful to you that you are powerful. Glory be to you for the age.
There isn't the clearly described unity within the mystical body of the Christ as Paul saw it. The imagery of the vine, I can see as being similar to that, to an extent, with followers likely being seen as its branches. But the imagery of the loaf seems not to describe a union with Jesus but suggests a union just with all the gathered believers.