I'm not sure which cracker species this is, but it was very beautiful for a butterfly lacking in colour. We scared it up from the path near the mango grove where it landed on a tree trunk; these butterflies typically rest on tree trunks head downward with their wings spread open.
They are called "crackers" because the males make a cracking sound when they dart out at passing insects. This may not be a male as I never heard it make a sound.

Edit: confirmed on iNaturalist as a Glaucous Cracker due to the chalky white patch on the hindwings.