My only addition would be...the earliest use of varnished cambric with flexible metal wrap I've seen is close to 1900 at the Dole Mansion in Crystal Lake, IL. He used European craftsman and probably had access to materials not generally available. I'm working on another home in the same neighborhood (and approx.time period) which has varnished cambric in conduit.
K&T was used in homes right up to the early '60's. when the acceptance of ground wires sounded the death knell to this method.
Romex first came out during the Depression, with paper around each insulated wire, and a cloth jacket over the whole. In the '60's, it was allowed to have a ground wire that was smaller than the conductors. Romex from this era will have a #16 ground wire.
My home was built in 1939 and wired with knob & tube - minimal wiring I might add. One overhead light in each room on main floor, one light on top floor, one receptacle in kitchen (for iron), one in living room (for radio).....all fed from a 30 amp 4 circuit panel. Wow, have things changed since then!
"Will it be cheaper if I drill the holes for you?"
Hey Dave, where is the Dole mansion? I left Crystal Lake when I was 13. I remember a Dole Avenue, where I used to mow lawns, just a block or 2 off Rt. 14 I think. Haven't been back there in almost 30 years.
Big John, there's a good book called "Old Electrical Wiring" by David Shapiro. It has a section of history and dating. Most of the K & T I have seen was from the 1800's till the early 30's, then it seems BX became the choice. Aluminum wire has been around since the 40's,but wasn't used widely till the 60's & 70's, mostly from 1965 to 1973, or the Vietnam years.
The reduced size neutral wire was available in the early 50s. The house my parents built in 1955 had it. I understand this was necessary to pass "GI Bill" inspection but that may not have actually happened outside the DC area.
Check your email BigB. Sorry I called you John(confusion with BigJohn). Check out Lakeside Legacy, which states the Dole Mansion was built in 1865, not 1900. Is it possible flexible varnished cambric was around in 1865??? It's a three story with basement & didn't appear that the wiring was added after original construction.
Dang, Daves working at the Dole Mansion. Last I knew it was a day care for children, somewhere to serve court ordered comunity service, and a half way house for drug addits. Not the best combination IMO.