Point a camera at the Milky Way from a dark site in Australia and the shape is unmistakable once someone has told you it is there. The Coalsack, the dark nebula beside the Southern Cross, is the head; the dust lanes running down through Scorpius and beyond are the neck, body and legs. It is a constellation made of the absence of stars, and it is read across the continent, by peoples with no common language and no shared ceremony.
It works as a calendar. When the emu appears in a particular orientation in the evening sky in autumn, the birds are laying and the eggs may be collected; later in the year the shape sits differently and the season has passed. The sky is telling people when to go and get eggs, which is a more practical use of a constellation than most cultures make.
There is a rock engraving at Elvina Track in Ku-ring-gai Chase National Park, north of Sydney, of an emu in a posture matching the sky figure, positioned so that the engraving and the constellation align at the right time of year. How deliberate that is has been argued about, but the engraving exists and the alignment has been measured.
Reading constellations from the dark rather than the light is shared with Andean tradition and with very few others. The two are entirely independent, and both worked out that in a genuinely dark sky the black shapes are as legible as the bright ones.