An Englishman made a single shot 2 bore in the 90's or early 2,000's, seems to me. I saw the video.

As far as in the 1800's, I've not seen any proof there was one.

Baker's biggest rifle was a 4bore. He thought to make it even more effective and had a 3-to the pound elongated hollow based conical made for it. In his own words, "'it' led me into such scrapes to which I eventually gave up the conical as useless" (for killing dangerous game).

In a ML, conicals have to be pure lead and as such, rivet on heavy bone or hard tissue, turn and do not follow a straight path through the animal.
Rounds balls of correct size can be made in any alloy and out-penetrate conicals.

I still have pictures of Big Dog, RIP friend, holding and shooting the big gun in my photobucket account, but they have copy-righted my videos stored there and will not let them be uploaded back to my computer - pictures yes.