What would be a good cartesian equation to represent the shape of a wine glass?

Question

I want to find the volume of a wine glass by using either the disk or shell method (solids of revolutions).

The wine glass doesn't have to be of any particular dimensions, however it should roughly resemble an actual wine glass.

The cartesian equation could just represent half of a wine glass (because the method of finding the volumes of revolutions would result in a full wien glass.)

Answer 1

How about this?

$$f(x) = \tan^{-1}(x)+\frac{\pi}{2}\;\;|\;-4\le x \le 4$$