Using a Parisienne scoop (melon baller) scoop out small balls from the watermelon. Discard all seeds. Cut the muskmelon in half.
Scoop out small balls from the centre, leaving a thick shell. Discard all the seeds. Put the melon balls in a bowl and place it in a refrigerator to chill thoroughly.
To make the dressing, take fresh orange juice in a bowl. Add salt, black salt, black peppercorn and lemon juice. Mix well. Add mint leaves and mix well. Place the melon balls in a serving bowl.
Pour the dressing over and serve immediately.