Musty smelling note

The musty smelling note can be found by inserting 100 numulites into one of the chests on the bottom floor on the castle found in the north of Fossil Island.

Transcript
A miraculous discovery today - a pool, capable of rapid calcification. One of the young stumbled into it, looking for refreshment. The look of terror in its eyes chilled me to the bone as its soft tissue grew rigid - it reached down to free its feet and it drowned in its own, solidified saliva. Its body serves as a powerful market of the dangers of this island. We have witnessed such things before, but never at this rate.