Mesua thwaitesii, is a plant species in the family Calophyllaceae.

[1] The Sinhalese people of Sri Lanka call it "Diya Nā - දිය නා".

[3] Timber, seeds and bark of Mesua thwaitesii is known to have Xanthones and 4-phenylcoumarins.

Kostermans and Gunatilleke et al. call the tree described in the Wikipedia article Mesua nagassarium.

These authors list Mesua ferrea as a separate species that is endemic to Sri Lanka and is a small, 15 meters high tree that grows near streams and in marshes in the Southwest of Sri Lanka, where it is called "Diya Na" in Sinhala, meaning "Water Na Tree".