3.5 pounds, literally nothing in a Bethesda game. :)
I dunno, since junk is now useful, I find myself quite regularly approaching my max capacity due to so many tin cans and things.
I definitely need to be more careful about what I pick up.
The ratio of weight to scrap is awful on some things though.
Also, since discovering that I can force any settler to equip what items I like (can't believe I missed the 'equip' button for so long), I have taken it upon myself to humiliate the weakest and most feeble members of my settlements.