Full Idea
In 1878 Cantor published the unexpected result that one can put the points on a plane, or indeed any n-dimensional space, into one-to-one correspondence with the points on a line.
Gist of Idea
Cantor proved the points on a plane are in one-to-one correspondence to the points on a line
Source
report of George Cantor (works [1880]) by Shaughan Lavine - Understanding the Infinite III.1
Book Reference
Lavine,Shaughan: 'Understanding the Infinite' [Harvard 1994], p.42