Resizeable (by drag) iFrame?

I’d like to resize my iFrame, ideally by dragging (although a big/small toggle would be ok too). But when I size-down the div, I just get scroll bars. I don’t see a ‘resize’ API or command. Is this possible some way?
image

This needs to be done on the embedding site. Make sure you pass 100% as the height and width parameters when creating the iframe.