Well, my post ("What is it we become a member of?") seems to have stirred the Walled Internet. Where do you go to know what our Universalist or Unitarian forebears thought membership meant? So long as you don't confuse the concepts of parish, society and church, you can look to a large, if disjointed, number of resources. And the idea of a meetinghouse being an entity, through trustees, in its own right. I do not intend to exhaust this thought here.
First, I'd look to service books and ministers' manuals, common after the first third of the nineteenth century. Look for services of opening churches and confirmation, which often includes language about membership. Also, Universalists published meaty apologetic works that often had a polity chapter, so you'd have all you need to start a church. Don't skip the introductions. Look for model bylaws and constitutions, especially among the Universalists; these are easier to find than the local bylaws, but some can be had. Not just for the church and the parish, but for the (after the 1890s) the recommended unified church-parish. And for the state conventions, and how the concepts of fellowship, obeying laws and assented belief have parallels at the local level. Look to the Universalist professions of faith without knee-jerk anti-credalism, such as the 1899 "Five Principles" which begin "conditions of fellowship in this Convention shall be as follows…"
Look to what made certain churches and leaders exceptions, so as to see the rule. The preface of the King's Chapel prayerbook is, among other things, an ecclesiological document. Investigate James Freeman Clarke's Church of the Disciples (I'll come back to him) and the institutionalism of Universalist Elbridge Gerry Brooks's "new departure."
Consider that the law itself has shaped our ecclesiology, even if we don't talk about it past the Cambridge Platform. There's the ad-hoc and minimalistic ecclesiology of first generation Universalists. The Dedham Decision, naturally. But also laws that forbade religious congregations from incorporating early on; what was their alternative? (Virginia was the last (PDF) give this up, in 2002.) And the very idea of tax exemption…
There's more, but that's enough to digest now.