Passage: As the air, Shu was considered to be cooling, and thus calming, influence, and pacifier. Due to the association with dry air, calm, and thus Ma'at (truth, justice, order, and balance), Shu was depicted as the  dry air/atmosphere between the earth and sky, separating the two realms after the event of the First Occasion. Shu was also portrayed in art as wearing an ostrich feather. Shu was seen with between one and four feathers. The ostrich feather was symbolic of lightness and emptiness. Fog and clouds were also Shu's elements and they were often called his bones. Because of his position between the sky and earth, he was also known as the wind.In a much later myth, representing a terrible weather disaster at the end of the Old Kingdom, it was said that Tefnut and Shu once argued, and Tefnut left Egypt for Nubia (which was always more temperate). It was said that Shu quickly decided that he missed her, but she changed into a cat that destroyed any man or god that approached. Thoth, disguised, eventually succeeded in convincing her to return.

Question: What type of feather has Shu been portrayed wearing?
ostrich