cubic egg

or

The curve can be seen as a linear distortion of an ellipse.
It has to be distinguished from another egg-formed cubic, Newton's egg curve.

The first form has been constructed by Fritz Hügelschäffer using two circles as follows:
Given a circle C₁ (the smaller one) formed by the points C (x₁, y₁) with center B.
And given a circle C₂ formed by the points D (x₂, y₂) with center A.
Then the cubic egg (black curve) is formed by the points E(x₂, y₁), assuming the points B, C and D are lying on a line.
Remark: the characters belong to the point in the left down corner of it.