Figure Eight Curve - MacTutor History of Mathematics

Lemniscate of Gerono - Wikipedia

Watt's Curve - MacTutor History of Mathematics

Lemniscate -- from Wolfram MathWorld

The Beauty of Geometrical Curves

Eight Curve -- from Wolfram MathWorld

Watt's curve - Wikipedia

Book : The Contact Patch

Graphs of Parametric Equations

Plane Geometry - Bruce E. Shapiro

External Influences on U.S. Undergraduate Mathematics Curricula: 1950-2000

Frozen Figure Eight

Figure Eight Curve - MacTutor History of Mathematics