Is the restriction on the amount of liquid in the container, or the size of the container itself?

The 3-1-1 page says:

Liquids, gels, aerosols, creams and pastes must be 3.4 ounces (100ml) or less per container

It sounds like it's on the amount of liquid, rather than the container itself.

I ask because I have a nice 4oz Nalgene travel container. What if I filled it half way up? That way, it's clearly less than 3oz, probably closer to 2oz.

Is the restriction on the amount of liquid in the container, or the size of the container itself?

The 3-1-1 page says:

Liquids, gels, aerosols, creams and pastes must be 3.4 ounces (100ml) or less per container

It sounds like it's on the amount of liquid, rather than the container itself.

I ask because I have a nice 4oz Nalgene travel container. What if I filled it half way up? That way, it's clearly less than 3oz, probably closer to 2oz.