Full Idea
The 'transcendental numbers' are those irrationals that can't be fitted to a suitable finite equation, of which π is far and away the best known.
Gist of Idea
Transcendental numbers can't be fitted to finite equations
Source
Brian Clegg (Infinity: Quest to Think the Unthinkable [2003], Ch. 6)
Book Reference
Clegg,Brian: 'Infinity' [Robinson 2003], p.69