In Egyptian Mythology, Nuit (Nut) was the name of the goddess of the sky, daughter of Shu and Tefnut, sister and wife of Geb, mother of Osiris, Set, Isis, and Nephthys. Described by Crowley in his Magick in Theory and Practice thus: "Infinite space is called the goddess NUIT." Nut was generally depicted as a woman with blue skin, and her body covered with stars, standing on all fours, leaning over her husband, representing the sky arched over the earth.
Her relationship to HADIT is an invention of Crowley's with no basis in Egyptology, save only that Hadit was often depicted underneath Nuit - one finds Nuit forming the upper frame of a scene, and the winged disk Hadit floating beneath, silently as always. This is an artistic convention, and there was no marriage between the two in ancient Egyptian legend.
SEE ALSO Geb, Horus (Hadit), Shu.
[Source: Shawn C. Knight, "Egyptian Mythology FAQ" ]