Resolvable vs Observable.
Well, here's a sketch done in 1855 by Sidney Phillip Coolidge of Saturn using the 15" Great Refractor of the Harvard College Observatory. The Encke division is certainly visually observable, as well as the Minima:
You should note that the orientation of the Rings in the above sketch is also very similar to their current orientation.
VERY important to note in the notes Coolidge made in 1857 about his observations of the B-Ring as being "streaky". This wasn't much picked up on until the 1970's and then only the confirmation of the the spokes in the B-Ring by Voyager. Coolidge had both a keen eye and one heck of a scope at his disposal!
This should ruffle some feathers!
You can find some more info on Coolidge and this sketch in these two links:
https://cseligman.com/text/atlas/sidneycoolidge.htm
http://ejamison.net/bond.html
In many photos posted here there is also a huge variation on image detail with the same scope but in different hands. There are currently two images of Saturn posted, both using a C14, one clearly shows the F-ring, and the other just, just barely visible. Yet both show a remarkable resemblence to the sketch above with the amount of detail Coolidge was able to pull visually. I wonder now if the F-ring is visible directly too?