How many?

Ounces

The ounce /ˈaʊns/ is the name of several different units of mass, weight or volume and is derived almost unchanged from the uncia, an Ancient Roman unit of measurement. The avoirdupois ounce (exactly 28.349523125 g) is 1⁄16 avoirdupois pound; this is the United States customary and British imperial ounce.

Slugs

The slug is a derived unit of mass in a weight-based system of measures, most notably within the British Imperial measurement system and the United States customary measures system. A slug is defined as the mass that is accelerated by 1 ft/s2 when a net force of one pound (lbf) is exerted on it.