It's 43C, and Professor Anil Gupta has been hiking the scorched plains of central India for hours. But he smiles widely as he enters a tiny village in search of another unsung genius.

"If you have any new ideas or you have any new inventions, I'm here to promote you," he tells farmers.

For more than two decades, Gupta has scoured rural India for its hidden innovations, motivated by the belief that the most powerful ideas for fighting poverty and hardship won't come from corporate research labs, but from ordinary people struggling to survive.

Gupta and his aides have uncovered more than 25,000 inventions, from the bicycle-mounted crop sprayer to the electric paintbrush that never needs to be dipped in a paint can.