Negative Share Prices in the mid 19th Century

I'm currently reading The Company : A Short History of a Revolutionary Idea. I'm already familiar with a lot of the history of limited liability companies in the U.S. and U.K., but here's an interesting tidbit:

In the mid-19th century, many companies were formed, and stock issued, without the investors paying the full par value of the shares they received. The investor was legally required to pay the rest of the par value only if and when the company would need it to meet its oblilgations. Thus, many near-bankrupt companies on the London Stock Exchange actually traded for negative prices (e.g. I'll give you 2 pounds per share if you'll take my shares from me). Even 150 years ago, markets were quite efficient.