In J.M. Barrie's Peter Pan, who is it that must sleep in a cradle?

When Wendy goes to live with the lost boys, she becomes
their mother and cares for them in every way. Though she fears she does not have the
qualifications, she quickly takes on the responsibilities that a mother would, including
darning their socks and scolding when necessary.

They have
many adventures, and Wendy is always there to keep house for them and tell them
stories.

One thing Wendy does is tell Michael he must sleep
in a cradle. He feels he is much too old for this, but Wendy says their home must have a
cradle and he is the smallest of the boys, so he must sleep in the
cradle.