In ancient times the bookends were made from very heavy materials to sustain the weight of the books, while the modern ones use a smarter technique: while they are light, they are shaped so that they can use the weight of the books themselves to anchor and sustain them. I call these "model T" and "model L", depending on their shape (resembling a T or an L).
I wasn't able to find much about their history, especially who invented these models and when: both wikipedia and another source vaguely claim that "it was patented in 1870s", but don't bother to say who patented that, which is the exact year, and if the model was T or L or a generic patent encompassing both.
Does someone have more information about that?