Assuming  the coffin was 6'6" long x 2'-6" wide x 1'6" deep, I figure it's surface area was 60 square feet (a little less than 2 sheets of plywood, for comparison).  Assuming the wood was 2" thick (actual, not nominal), that makes 120 board feet, or 10 cubic feet.

The problem is that Graphic Standards (or the copy I just mooched, at least) doesn't give the cubic foot weight of mahogany.  The heaviest wood they do list is white oak at 47 PCF; the lightest is cedar at 23 PCF.  If we assume that mahogany (which is not terribly dense and heavy) weighs 38 PCF, that would give a coffin weight of 380 lbs, which seems reasonable (but I suspect still high).

For the coffin to weigh 700 lbs with him in it, and assuming he was down to 150 or so following lengthy illness, that means the wood would've had to be 2.89" thick, which seems really excessive.

I would think the wood wouldn't have been more than 1.5" actual, which means the coffin weighed 285, and we'll throw in another 15 lbs for satin and pillows and clothes (but no shoes! Or do rich people/US Presidents get buried in their shoes?), so we'll call the coffin 300.

If we figure the coffin weighed 250, that means the wood would be 1.3" thick, which sounds substantial without being wasteful.  I vote for the 250 lb coffin.

Anybody want to check Gates, Kingsley & Gates website and see what their coffins weigh and go for?

Sign me,

Mike Math

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