³We may prove this mathematically by algebraic substitution. Given that the total mass (m) of any liquid sample is equal to the product of that liquid’s mass density and its sample volume (m = ρV ), that volume (V ) for any vessel of constant cross-sectional area (A) is given by the expression V = Ah, and that hydrostatic pressure is equal to P = ρgh, we may combine these three equations to arrive at m = AP g . This final equation demonstrates how the total mass of liquid stored in a vessel (m) of constant cross-sectional area (A) is directly proportional to pressure (P), and independent of density (ρ).