Of Anakin Skywalker, Obi-Wan's Force Ghost had the following to offer:
He’s more machine now than man. Twisted and evil.
Obi-Wan may have been remarking upon Vader's lost humanity more than anything else, but it got me thinking about Vader's physical being anyway. Exactly how much machine and how much man are we talking about?
We get some idea from the surgery scene in Revenge of the Sith:
But things may have changed for Vader in the years between Revenge of the Sith and Return of the Jedi, such as organs failing and needing to be replaced, as well as improvements to his technological components.
The question is:
At the time that Obi-Wan made his comment (which was in Return of the Jedi ), what was the ratio of man to machine in Vader?
Well-reasoned estimates are welcome. Ratio by volume is preferable, but weight is fine too, so long as this is made clear in the answer.