Note: This information was taken from TSR's original AD&D adventure, the Temple of Elemental Evil.
POUCH OF HOLDING

These apparently normal leather or cloth pouches are found in groups of 3-6 (1d4 + 2) attached to a belt. Each pouch can hold 100 gp (or ten pounds weight) as if it were but 1 gp (or a tenth of a pound). However, nothing larger than 1 x 2 x 3 inches can fit into a pocket, and the maximum cubic volume capacity for a pocket is 3 x 6 x 12 inches. (Thus, vials of holy water would easily fit, but a dagger or wand would not, in most cases.)