271873
His friendship with Gairdner led to his acquaintance with Ralph Waldo Emerson , who in 1833 came to Edinburgh : theirs was a lifelong friendship .
 Ralph Waldo Emerson
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Ralph Waldo Emerson