It always amuses me when a young child is given an expensive present and they are more interested in the ribbon / tissue paper / box it came in.
There are so many plastic baby toys in the shops but babies can actually find these quite boring and prefer things which are interesting to touch and look at. Plastic toys don’t always stimulate a baby’s senses in the same way everyday objects do, because plastic toys generally all smell, taste and feel the same.
Treasure baskets are baskets or boxes you can put together yourself, full of interesting household objects with various shapes and textures for baby to explore (wooden spoon, pine cone, leather wallet, ribbons, etc). Obviously babies should not be left unsupervised with anything which is not meant to be a toy, but they should be allowed to explore the objects without being shown what they should do with them or which object they should pick up next, as the idea of treasure baskets is to let the child make their own choices. Make sure everything is clean and nothing is broken / has sharp edges or is small enough to choke on and sit close by so you can step in if you need to.
Interestingly, the only thing in this basket that my son didn’t try to eat was the apple!