Jules Stewart 
Spying for the Raj [EPUB ebook] 
The Pundits and the Mapping of the Himalaya

In the 1860s, Captain Thomas Montgomerie trained natives to be surveyors, and had them explore the region covertly. These men, known as pundits, were disguised as lamas (holy men). This book talks about these servants of the Raj who managed to map the Himalayas and Tibet, helping the British to consolidate their rule in the Indian sub-continent.