Peel the eggplants and cut them into round slices, 1/2″ (1 cm) thick. Salt them and leave them for a few hours. Discard the water and wash them.
Arrange in a suitable pot and pour on a mixture of the water and vinegar over them. Boil until softened.
Pour in 1 tbsp oil every 2-3 layers. Once you're filled the jars, pour in a final 1 tbsp oil on top. Close with caps and store in a cool area.