The Mystery Bag is a classic Montessori Sensorial activity, used to train the ability to recognize objects by touch and movement alone (without the eyes). While we didn't do the exact lesson, it is quite Montessori-inspired.
The first bag we did used shapes as Ty is certainly familiar with the basics. We examined and felt them then placed them in the bag. I did a quite exaggerated demonstration first, wiggling my hand around, exclaiming that I had found something, then letting Ty know that I was moving it around in my hand to figure out what shape it was. After my guess I removed each shape and confirmed...or found a mistake. Once in a while I do like to purposely make an error to give Tyler a sense that it's okay to not be perfect. He delighted in this, saying "Silly Mama!" with a big smile.
Then it was Tyler's turn. Sometimes he pulled shape right out, sometimes he guessed beforehand. I playfully asked "What did you find?!" when he had hold of something to serve as a reminder to feel and name the object first. It worked.
The next set of objects was much more fun. We used items that Tyler handles on a daily basis or objects that he is very familiar with. He was excited by them all and couldn't wait to get them into the bag.
After a little practice with the shapes, he was much better about feeling and naming before taking the objects out. They were also easier to discriminate than the shapes.
We used these objects at least four times, with Tyler excitedly putting them back in the bag to play again each time he completed the work. This will be one to do again and again with various objects for sure!