Thanks for the reply Mr. Smarty Pants. However, I am still not convinced by your arguments.
a) my cat was extremely independent and hated being picked up and when I occasionally did he struggled in a most UNwilling manner. So presumeably according to your argument that would have made him heavier. Nevertheless, that was the weight I had to go by. 9 pounds on the scale at the vets.
b) while alive he certainly did have muscle tone to keep his shape, however, shortly after death--the time which I am curious about--during which he felt so VERY much heavier--his body kept its shape even better--as rigor mortis had set in.
So your analogy of his dead weight to a loose bag of dry cement is not a parallel.
However, I am still willing to be convinced. And I return to my original question--do you, or anyone else, know of any actual scientific research in which a body--human or animal--was weighed just before death and again after death--and I will add the proviso that it should be when rigor mortis has set in. And what was the result.
Etymologically the phrase can be traced as far back as 1650 (
http://www.etymonline.com/index.php?search=dead+weight). So I would assume that since at least then people were noticing that dead bodies felt heavier than live ones. I I still need to be convinced by further arguments than the ones you have presented thus far that it is simply a matter of perception and not an actual weight change.