text: Its not water, but Li Bing developed a process for extracting this commodity from wells.
full_question: Its not water, but Li Bing developed a process for extracting this commodity from wells. Huo Guang initiated a series of debates, or "discourses," about a Han Dynasty monopoly on iron and this commodity. The Great Hedge of India was planted along the Inland Customs Line to facilitate the collection of a tax on this good. A nonviolent protest was planned for a center of this commodity's production at Dharasana, but its leader was arrested a month after he arrived in Dandi. For 10 points, name this good whose taxation was protested by a Mohandas Gandhi march.
first_sentence: Its not water, but Li Bing developed a process for extracting this commodity from wells.