Paul Conley was kind enough to send me this article from the September 18, 1860 edition of the St. Louis Daily Bulletin.
A couple of things to note:
-Merritt Griswold, in his letter to Al Spink, mentions four baseball clubs by name (the Cyclones, Morning Stars, Empires, and Commercials) that were in existence in 1860 and this article states that there are "five or six clubs in existence" with more forming.
-The article states that the clubs had "from thirty to forty members" which, to me, seems to be within historical norms. My understanding is that most Eastern clubs had two or three nines, which would mean twenty-seven members. Add in a few subs, extras, or non-playing members and you easily get to thirty members. Forty members, which seems a bit large, would get you four nines plus.