OK, just to spell it out:
A rule of thumb for jet airliners:
The additional fuel burnt in order to carry additional load on board the aircraft is approximately 2.5% by mass of the extra load carried, per hour.
Carrying an extra 100kg would increase your fuel burn by approximately 2.5 kg per hour.
SEP manual = Safety and Emergency Procedures manual.
Our manuals are approximately A5 in size, a couple of inches thick and with the consistency of a telephone directory!
I did not include the Tech Log or Certificates File in my guesstimate because for regulatory reasons those must be hard copies.
My current type is B737NG.