What defines a nation? It's a question that Australia, as a young country, is constantly trying to answer. An exhibition that just opened in Sydney attempts to explore how Australia's past has forged its present. National Treasures is a collection of nearly 200 manuscripts, drawings, maps and objects gathered together from state and territory libraries. Starting with the very earliest depiction of the Southern Cross constellation, by a Spanish explorer in the 16th century, it gallops through Australia's convict origins to the present day. Whether a collection as varied as a cricket bat once owned by sporting hero Don Bradman, wine labels from the 1970s, and paintings on Japanese toilet paper by prisoners of war truly encapsulate the 'Australian character' is questionable. But the exhibition features much of the collective cultural baggage that looms large in the minds of most Australians. We are reminded how inauspicious were the country's beginnings. When the then Lieutenant James Cook set sail for the southern ocean from Britain in 1768, the ostensible purpose of his expedition was to observe the transit of Venus. But he carried with him secret instructions from the admiralty ordering him to lay claim to any land he came across 'with the consent of the natives'. But native consent was conspicuously absent when Britain established its penal colony in Sydney in 1788. There are some compellingly gruesome reminders of those early years, including the only surviving, complete convict uniform. Its black and yellow harlequin design was intended to humiliate prisoners, similar to the bright pink jumpsuits some US felons are made to wear today. A set of leg irons from the 1840s would have 'rubbed the skin raw', we are told, and could have weighed a fearsome 32kg. Not surprisingly for a nation founded on notions of crime and punishment, the line between hero and villain has often been blurred. One of the most popular exhibits is the home-made, bucket-shaped helmet worn by the bushranger (outlaw) Ned Kelly in his final encounter with police at the siege of Glenrowan, Victoria, in 1880. Raised in poverty and bullied by authorities, Kelly to many Australians is a folk hero akin to Robin Hood. To others, he is a murdering sociopath who killed policemen in cold blood. The debate still rages. The evolution from a British to an Australian identity is illustrated by early cooking guides. The English and Australian Cookbook, written by a wealthy Tasmanian landowner, was the first to embrace ingredients such as mutton bird, wombat and black swan ('when young they are tender'). One uniquely Antipodean recipe, called Slippery Bob, was a stomach-churning conglomeration of kangaroo brains, flour, water and emu fat. It is one 'treasure' that Australians would probably rather forget about.