Hervey stole the mummy and also the copy of the manuscript which was written in Latin.
He sent this latter to Braddock--who was then at Cuzco--as an earnest of his success in procuring the mummy, and when the Professor returned to Lima the mummy was to be handed to him.

Unfortunately, Braddock was carried into captivity for one year, and when he escaped Vasa had disappeared with the mummy.

As the Professor had deciphered the Latin manuscript, he knew of the emeralds, and for years had been hunting for the mummy--sure to be recognized from its peculiar green color--in order to get the jewels, and thus secure money for his Egyptian expedition.
All through, it seems, the Professor was actuated by purely scientific enthusiasm, as in the abstract he cared very little for hard cash.
Bolton told Mrs.Jasher that Braddock explained how much he desired to get the mummy, but he did not mention about the jewels.

For a long time Sidney was under the impression that his master merely wanted the mummy to see the difference between the Egyptian and Peruvian modes of embalming.
Then one day Sidney chanced on the Latin manuscript, and learned that Braddock's real reason for getting the mummy was to procure the emeralds which were held in the grip of the dead.

Sidney kept this knowledge to himself, and Braddock never guessed that his assistant knew the truth.
Then unexpectedly Braddock stumbled across the advertisement describing the green mummy for sale in Malta.