Is it possible to prevent content affecting the width of it's floating container

I have a floating container width an image and caption inside. I want the image to dictate the width of its container, and for the caption to wrap onto multiple lines if required. Is this possible without explicitly setting the width of the container itself?
See here for a little explanation/demo.
Any help would be much appreciated, I'm new here!

//mod edit: A link must include the protocol token, "http://", else it will be taken as a relative address. Fixed. ~gt

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