On the plane yesterday I was reading Thomas Hardy's Far From the Madding Crowd (thanks Bessie!) and came across the following phrase:

Indeed, he seemed to approach the grave as a hyperbolic curve approaches a straight line -- less directly as he got nearer, till it was doubtful if he would ever reach it at all.

What proportion of readers in 1874 would know what a "hyperbolic curve" looks like? How about readers today? This would be a good Fermi problem...

In another passage Hardy refers to "the accuracy of pure mathematics." It appears he had a fondness for the subject. :)