I watched an episode quite a long time ago and was facinated to hear that apparently Florence Nightingale invented bar charts. I found it interesting that it was in the early 1800s that bar charts were first used.
Well apparently William Playfair preceded her significantly with a published barchart in 1801, which given Florence Nightingale was born 1820 was defintely ahead of her.
QI how could you, actually I have always wondered about some of the facts that make it on to QI, perhaps I should research more.
For anyone interested in early visual representations of information then I found this site particularly interesting.