Superscript three
On Windows, hold Alt and type 0179 on the number pad, then let go of Alt.
Copy it
About the superscript three
A small raised three means cubed: cm³ is a cubic centimetre, and x³ is x multiplied by itself three times. Latin-1 included just three raised digits, ¹, ² and this one, which is why it is easier to type than ⁴ or ⁵.