I haven't seen video of one a black mass but I'm sure we've all heard that it's part of that ritual to reject the emblems as well, which is creepy, and makes you wonder if Anton LaVey took the idea from the witnesses!! lol
I really enjoy reading about the early Watchtower history now as well ironically that's how I found the Berean Bible Students in Lombard, and have enjoyed their association and the fact they won't invade your life.
A really good history book that covers the first 3 presidents of the org is Tony Wills - A People For His Name and of course Jim Penton's - Apocalypse Delayed. Lots of interesting characters in those early days, P.S.L. Johnson and his antics in England which unfortunately was the catalyst for Rutherford takeover, W.F. Salter in Canada trying to take the branch's assets and sending letters to congregations worldwide in the name of the Org, and E. C. Henninges and the New Covenant schism and him actually walking away the the Orgs Australian assets and most of the Australian "ecclesia" leaving.