Lightning flashes. Rain slants across the jungle in fine silver streaks. Leaves whip in the wind. In the middle of it all, a tiger crouches, startled — about to pounce, or about to bolt.

This was Henri Rousseau's first jungle painting, shown in Paris in 1891 with the title Surprised!. Critics laughed at its flatness and its odd perspective. One reportedly suggested it was painted by someone with their eyes closed.

Rousseau had never seen a jungle; his plants came from Paris greenhouses and his tiger from pictures and visits to the zoo. But the painting's energy is unmistakable, and within a couple of decades younger artists — including Picasso — were treating the self-taught customs officer as a genius.