On: 2+1=4, by quinoa

[dmoy]

Trivially, you can also just cook some rice on the stove, verify that rice is not spherical, and also verify that it gets significantly bigger. (Like 3x bigger per dry rice unit of volume, and you don't (usually) cook water:rice 2:1 for most rices)

[sitkack → dmoy]

Whom among us has not overflown a rice pot on the stove?

[sukilot → dmoy]

2:1 is quite common, because it's simple, despite being not great, especially as amount cooked increases.

Rice isn't speherical, but it isn't a perfectly packed crystal either.

Unless you think air fills up inside each grain, the volume from "air" is the packing volume.