Queen Mayadevi (also Maya or Mahamaya) was the historical mother of Sakyamuni Buddha. She died not long after his birth, but is believed to have been reborn in one of the heavens where he later manifested and taught her the Dharma so that she too became enlightened.
She is traditionally depicted just as she was about to (painlessly) give birth, standing and holding the branch of a tree in her right hand.
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