Precious little info remains about the trials bikes - the builders didn't share much of the info with the public and their competition... Bikes for the public often were light, but not insanely so - they usually were durable. Look at Herse cantilever brakes, and you see what I mean. (A Singer or Herse randonneur, fully equipped with racks, lights, fenders, triple cranks, etc. in a 59 cm size weighs about 23-25 lbs. depending on specification.)
The bike weight in the trials, however, was independently checked - I have a photo (to be published) of Daniel Rebour looking on as a bike is weighed at one of the trials. So what the makers said didn't matter - the scales showed the truth.
The point was to advance technology by pushing the envelope. That said, very few bikes seem to have been penalized for breaking stuff, so they did last at least one grueling event. Ernest Csuka told me the bikes weren't much fun to ride, with serious shimmies on the downhills.
As was pointed out earlier on the list, every part was modified. It was an insane amount of work, but the publicity from winning the trials was worth it.
More recently (1970s or 80s?), Csuka/Singer built a racing bike that is still on display in the shop, with Reynold 753 0.4 mm tubing (butted thicker at the ends), CLB brakes, etc. that reportedly weighs 7.8 kgs (17.16 lbs.) - but no independent check for this one. This one has only widely available components, but of course no racks, fenders and lights.
Jan Heine, who doesn't care about weight all that much in Seattle