Why Does this Painting Show An Ostrich Egg Hanging From the Ceiling?

Hidden symbols in the Brera Madonna by Piero della Francesca

Brera Madonna (1472–1474) by Piero della Francesca. Tempera on panel. Pinacoteca di Brera, Milan. Image source Wikimedia Commons

What is immediately gripping about the Brera Madonna, painted by Piero della Francesca in around 1474, is the elegant sense of space the artist has created.