LOL, you sound skeptical.
Almost anything would work. You could even use rope and wouldn’t need tools or nails, but 1x4’s would be fine, though personally I’d want something a little stouter, spaced a foot or so apart and you’d be good to go. It’d all fit in a small backpack and weigh almost nothing. It’s not rocket science.
I wonder how a Tree Climbing seat would work on them vertical pipe looking things??