How do you measure rainfall?

[Enola Straight]

I just saw Cecil's explanation how they measure snowfall...
They pretty much just stick a ruler into the snow.
But how do they measure rainfall?

[Shiva]

Um...

They stick a ruler in a can. It's called a rain gauge.

http://www.fi.edu/weather/todo/r-gauge.html

[SmackFu]

It can be a little more complicated than that. The official rain gauges have a funnel on top connected to a smaller graduated-cylinder-like measuring part. This lets them be much more precise in their measurements.

See: http://www.usatoday.com/weather/wrngauge.htm . It's striking how much those pictures look like "a ruler in a can" though.