After obtaining access to the Arcane University (to do so you must join the Mages Guild), buy two cheap bound weapon spells. You can get the Bound Dagger spell from the Discount Spells shop in the Imperial City's Market District. Make the second spell you purchase bind a weapon that you want to keep. Go to the Arcane University's Praxographical Center (northeast corner) and create a spell that does Bound Dagger for one second on self. You can repeatedly use this spell to raise your Conjuration skill above level 25, a level you'll need to achieve in order to get the free weightless Daedric weapons. Once your Conjuration is at level 25 or higher, make a new spell that will cast Bound Dagger and Bound "whatever weapon you want." (If you don't see the option to create a spell that does anything other than Bound Dagger, you'll need to make sure that you can actually cast the other bound weapon spell. If you can't, raise your Conjuration skill even higher.) Make sure that you add the Bound Dagger effect first, then add the second bound weapon effect. Set both effects for a duration of one second. Cast the spell you just made and wait for the sound of weapons equipping. Immediately go to your menu and you'll see that the second bound weapon appears in your inventory. Simply drop the weapon and you can then pick it up to keep forever. The weapon has no sell value, but it's weightless and pretty powerful. This glitch can be repeated as many times as desired, giving you access to an unlimited number of Daedric weapons.