Explanation: In the 19th century, Egyptian mummies that were found in the course of European archeological expeditions were sometimes sold off. Some would be acquired by collectors, others… ground up for use as paint or quack ‘medicine’.

… it was not the best of times for European archeology, a then-new discipline.

Using them as furnace fuel for steam engines (trains) even, especially smaller animal ones.

We usually source the cheapest possible energy dense material for solid fuel. That doesn’t seem either. Do you have a source?