Value in historical documents for city planning

 Bloomberg reports that Mumbai, "Mumbai Facelift Is Inspired by 200-Year-Old New York Blueprint," wanting to rework its urban form to better reflect its status as a South Asian financial center, is starting by reviewing the 1811 Commissioner's Report on NYC (Manhattan), which calls for a grid of blocks and streets.  

I myself utilize "old reports and documents" to inform my work, such as the 1980s plan for Central Park in NYC, or the Urban Design Plan for Manhattan, which dates to 1969.

New doesn't always mean better.

It's not a capital per se, but plans for Ottawa, Ontario and DC are relevant too.

WRT Mumbai, they should also look at writings about Haussman's plans for Paris, the 1907 McMillan Plan for Washington (never passed into law), and the earlier L'Enfant Plan.

Plus other plans from leading cities, including various iterations of the Regional Plan Association for New York City, preferably before the automobile became the primary mode of transportation and more modern work about pedestrianization and sustainable transportation, plus the impact of climate change on a city that already deals with super hot temperatures.