Can I tie a queen mattress down on top of my car?

This maybe a stupid question, but it s for the sake of not paying my fiancés step dad to haul a queen size mattress in a gas guzzling truck, but I own a 2004 Honda Crv and if it helps with any laws I live in Arizona. I want haul a queen size on top of my car. I have no rails on my car also. First of all is it legal for me to haul that size mattress on my car and if it is how would I tie it down? Thanks for any help. Just wanting to make my our move simple.

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