How can I get a widget to stay at the bottom of the sidebar!?!

This might be a silly question, and forgive me, but I am trying to see what CSS settings I can use to get a widget (text widget) to float at the bottom of the sidebar in this theme. I have tried looking for this information, and testing a few things, with no luck. I would love another head to bounce ideas off of.

Thanks.

P.S. The widget has a specific div ID, #text-3 to be specific, so I should be able to assign CSS to this widget and not affect the other text ones being used.