I use a coffee can - plastic or metal in the classroom. I send home a paper lunch bag with the instructions taped with wide tape on the outside of the bag. When the child brings the bag back I transfer the item to the can. Too many cans got lost or the lids got lost. The bags fair better in traveling and are easier to replace if they don't come back.
Guessing can at group time:
Sing: What's in the guessing can, the guessing can, the guessing can? What's in the guessing can? I don't know.
Have the children repeat "Will it break it if you shake it?"
Have the child who brought the item answer "Yes or No".
If it won't break, ask the child to shake it up and down and then side to side. Tell the child to ask the other children 3 questions:
"Does it sound hard or soft?" "Does it look heavy or light?" "Does it sound big or small?"
Allow time between each question for the other children to answer. Ask the children to give a thumbs up if they think ____________ (whatever is the right answer) is the right answer.
Tell the child to repeat the clues one at a time and allow the children to guess between the clues. Once they guess right, open the can and allow the child to walk around showing the other children what the item is.
Estimation Jar note - (5 listed) cut and put inside a clear plastic jar/container and send it home with a different child each day. Older children can go around and ask each child for their estimation and then write it down on a chart. Teachers can help younger children record the estimations. Have extra notes on hand to put back in jar because some children will not return the note. For preschool children I limited the number to less than 10, then as the year progressed I set the number to 20,etc.