Definition:Geometric Mean/Mean Proportional/General Definition/Historical Note

Historical Note on General Mean Proportional

This extension of the definition of a mean proportional is never made specifically in Euclid's The Elements, but introduced without definition in Between two Cubes exist two Mean Proportionals.

In the words of Euclid:

To three given straight lines to find a fourth proportional.

(The Elements: Book $\text{VI}$: Proposition $12$)