Vitruvius Quote

Pozzolana.—There is... a kind of powder which from natural causes produces astonishing results. It is found in the neighborhood of Baiae and in the country belonging to the towns round about Mt. Vesuvius. This substance when mixed with lime and rubble not only lends strength to buildings of other kinds, but even when piers of it are constructed in the sea, they set hard under water.

Chapter VI "Pozzolana" Sec. 1 - De architectura (The Ten Books On Architecture) (~ 15BC) - Book II