Chaldron

A chaldron (also chauldron or chalder) was an English measure of dry volume, mostly used for coal; the word itself is an obsolete spelling of cauldron.

[1] Many attempts have been made to calculate the weight of a Newcastle chaldron as used in medieval and early modern times.

Coal industry historian John Nef has estimated that in 1421 it weighed 2,000 lb (907 kg), and that its weight was gradually increased by coal traders due to the taxes on coal (which were charged per chaldron) until 1678, when its weight was fixed by law at 52+1⁄2 long hundredweight (5,880 lb; 2,670 kg), later increased in 1694 to 53 long hundredweight (5,940 lb; 2,690 kg).

[2] The chaldron was the legal limit for horse-drawn coal waggons travelling by road as it was considered that heavier loads would cause too much damage to the roadways.

Unscrupulous merchants would purchase their coal in lumps as large as possible then sell them in smaller sizes.