Leonardo da Vinci was born the illegitimate son of a small-town lawyer, yet he went on to paint the Mona Lisa, invent the parachute and map the workings of the human heart.

What made him so brilliant, so different from the rest of us? For the first time, 60 rare pages of his notes offer an unrivalled glimpse into how his mind worked.

When you walk into the Victoria and Albert Museum's new show on Leonardo, you expect to see the preparatory drawings for the Last Supper, or perhaps the famous Vitruvian Man outstretched in a circle and square.

Instead, you face page upon page scribbled with his mysterious mirror-writing; an onion sketched next to the cross-section of a human brain; a spiral staircase outlined next to a pump.

Boring? Disappointing? A bit loopy, even?

Only if you fail to look deeper.

Tough show

This show is much tougher to understand than the legions of past Leonardo exhibitions, admitted Professor Martin Kemp, the curator. "No-one has confronted the more difficult drawings, where he is literally in the laboratory of thinking."

The display does not look at Leonardo's art or inventions, but at the thought processes behind both. "Anyone wanting to understand the workings of Leonardo's mind should turn to these notebooks," Kemp said.

Here you witness the birth of some of his greatest ideas. What started off as a dissection of a bird's wing later became a flying machine. Leonardo drew the bone structure of the wing alongside that of a human arm, noticed the similarities and inferred that humans, too, should be able to fly with the right equipment.

It is this type of thinking that caused him to conceptually invent the helicopter, an army tank, a submarine, the use of solar power and the calculator - centuries ahead of their time.

His anatomical studies were just as advanced. As an artist, he was given permission to dissect no fewer than 30 human bodies over three decades. From a dissection of an ox heart, he deduced by thought alone how the flow of blood opened and closed the aorta ventricle (see picture). Leonardo used the idea to design a valve model, which was built for this exhibition.

Five hundred years later modern images of a beating heart have proved him right. "Not only was he right, but he was stunningly accurate," said Dr Francis Wells, a heart surgeon at Papworth Hospital in Cambridge.

Yet in his own lifetime most scientists ignored the self-taught Leonardo, as he lacked a formal education in Latin and mathematics.

Search for truth

Despite his genius, even Leonardo got it wrong sometimes. As drawn, the wheels of his army tank would have gone in different directions. And he quickly abandoned his designs for perpetual motion - objects that move forever without external energy - as "vain chimeras" on par with alchemy.

But he never stopped searching for truth. "Tell me if ever a thing were done," he wrote below an incomplete mathematical puzzle in one of his notebooks.

Ultimately, Leonardo's childlike curiosity about the world around him was at the heart of his genius. Like a three-year-old, he kept asking: "Why?"

It was his quest for answers that made Leonardo so unique, Dr Wells said. "Even today most of us read what is in books and we reproduce it, and if we're lucky, a bit later on we think about it and revise what we've learnt."

Leonardo "couldn't go anywhere without asking questions", Mr Kemp added. Everywhere he went, he scribbled down his answers in the pocket-sized notebooks he constantly carried with him - three of which are on show.

Along with the V&A's Forster Codices, as the journals are known, the exhibition also features drawings lent by the Royal Library in Windsor and the British Museum.

Animations

The drawings are brought to life by four animations projected against the walls. Animator Steve Maher, of Cosgrove Hall Films, explained how sequential figures of workmen drawn by Leonardo blended seamlessly into a film, demonstrating the 16 century master's grasp of motion. "I didn't have to do very much work on it," Mr Maher said.

A handful of models built after Leonardo's designs are displayed elsewhere in the museum with free access. In the foyer, Leonardo's hang-glider and parachute hovers above a prototype tank and a giant crossbow.

But the paid-for exhibition itself is not the visual and interactive spectacle offered by museums targeting young visitors.

This is an intellectual exercise. It requires you to study his drawings, read commentaries and listen to the audio-guide (without which much of the show is lost).

If you are not up for a mental gym, avoid this display. However, if you want to step into the mind of a genius, book your ticket now.

  • Leonardo da Vinci: Experience, experiment and design, V&A museum, London, 14 September 2006 - 7 January 2007. Admission fee.