Horizontal Site with unknown post widths

I’m trying to make horizontal scrolling site. I’ve found lots of ways to accomplish this but all of them involve knowing either the wrapper’s width or the post’s width. The site I am creating is a portfolio site and I will not know the width of each post.

Can anyone thinking of a way to make a site scroll horizontally without knowing the wrapper or post width?

Test url: grillo.madebyjesse.com then click Case Studies