Very young infants cry when they feel discomfort from hunger, pain, feeling too cold or too warm, sudden changes in position, transitional times, and too much stimuli from environment. Respect the child’s right to express feelings, or moods, whether crying or smiling. Try to find and eliminate discomfort.
Original RIE Manual
Toys should be sturdy but simple. I do not like busy toys. I like busy children manipulating their toys in many imaginative ways. Include objects that are safe and simple. These objects should be basic, able to be manipulated in many ways, and not requiring adult help or supervision. They should require the child to be active, not passive.