Googling "British cutting the thumbs of Indian weavers" gives several links.
From the Telegraph-Calcutta:

Found: Raj-razed town
The British had chopped off their forefathers' hands in Bengal a generation ago, so the weavers of Mahua Dabar in Awadh cut off a few British heads during the turmoil of 1857. Erased from the face of the earth by the Raj's revenge, this lost town has been found again thanks to one man's effort, reports Tapas Chakraborty

George Monbiot recites the story and immediately afterward cites Kicking Away the Ladder: Development Strategy...by Ha-Joon Chang:

India gets serious on climate change  Guardian

Indians are also painfully aware that the rich nations in the past deliberately prevented their nation from developing. England, for example, banned the import of calico (cotton cloth) from India, in order to protect its own textile industries. It went on to smash Indian looms and cut off the thumbs of Indian weavers in order prevent them from making their superior products. As Ha Joon Chang shows in his book Kicking Away the Ladder, England's industrial revolution was made possible by preventing India's. Many people there suspect that attempts to limit India's future greenhouse gas emissions have the same purpose. (I may well buy Kicking Away the Ladder which may or may not document the incident)

Indian Models of Economy, Business and Management - Page 42 by Kanagasabapathi (Google books) extends and provides a source for Chang's quote:

(H H) Wilson made it clear when he wrote that the British manufacturer "employed the (arm of political injustice to keep down and ultimately strangle a competetor with whom he could not have contended on equal terms...They even took the extreme step of cutting off the thumbs of weavers..."

This appears to come from The History of British India by James Mill and H H Wilson pub. J. Madden, 1848. H H Wilson was an Orientalist and became a scholar of Hindi literature while in India working for the British East India Corporation, and who extended Mill's work posthumously.

"It is not necessary to have hope in order to persevere."