How many waters are necessary to dissolve a rock salt molecule?

It is textbook knowledge that in order to dissolve rock: salt in liquid water at ambient conditions at least nine water molecules per salt molecule are needed. An Obvious but until now unsolved question arises: How many water molecules are necessary to solvate a Single sodium chloride molecule? In other words, what is the smallest water cluster in which a solvent separated Na+/Cl- ion pair becomes stabilized? The answer, based on accurate quantum chemical calculations, is that simple extrapolation from the liquid is quantitatively wrong and that the hexamer represents the smallest water species that dissolves the NaCl molecule.