More than a few ounces - The listing on Amazon says that it's 1.68 pounds!
But if you must, this one is "only" one pound.
Amazon.com : Microfiber Surf Beach Wetsuit Changing Towel Bath Robe Poncho with Hood-One Size Fits All : Sports & Outdoors
www.amazon.com
At least six valid uses come to mind for the above listed product. This well exceeds the pilgrim's rule-of-thumb that: 'every item you carry must have two uses.' N.B. It even comes in assorted colors - I like the grey to hide light dirt.
Here are the uses I came up with.
1. The obvious - a means to strip naked and change in the middle of an occupied albergue room - on your way to, or to get dressed after bathing. It does make a good "all over" towel - including for longer hair. If it gets wet, it will wring out and dry fast.
2. It will make a good roll and stomp towel to dry your hand washing faster. Lay the tunic flat on a bunk, layout the clothes you just washed and wrung out and need to dry. Roll them up. Stomp, walk all along the roll on a floor. This removes excess water from the washed clothes. Unroll the clothes and hang to dry. Hang the tunic towel to dry.
3. As a wall or privacy shield between albergue bunks that are too close together. Attach it to the bunk bed above you with clothes pins, bulldog clips or duck tape. This assumes you have a bottom bunk. In all but the hottest weather, this creates a 'pullman berth.'
4. In lieu of a fleece jacket (to offset weight), it could be worn for warmth. The medieval pilgrim wore a similar tunic with a rope 'belt' - and not much else.
5. You can sleep in it. Add socks and you would likely be very comfortable. You might / could skip the liner or sleeping bag in very warm weather.
6. Under a full rain poncho to keep you warm, but still provide ventilation superior to a regular fleece jacket.
So, someone needs to try it and report back.
Hope this helps the dialog,
Tom