{Joining the new fad for wearing Class hats, in 1900}
Public Domain - Out of copyright.
Source: Princeton University, The Class of 1895, Record of the Class of ’95 of Princeton University 1895-1900. Edited by the Secretary, Andrew Clerk Imbrie, Number Three, New York, Cooke & Fry,1900. Courtesy HathiTrust.
A year after the Class of '96 had instituted Class hats in 1899, the Class of '95 donned white pith helmets resembling ones then being worn by British troops in the Boer War. Classmates called these their "Lord Metuchen" helmets. The term was a New Jersey-centric pun on the name of Lord Methuen, a senior British commander much in the news back then.
The photo also shows (upper right) two of the "Japanese parasols" that classmates carried in that year's P-rade (somewhat incongruously, since they were already wearing sun helmets . . . ).
Note: Go here for the story of '95's contribution to the 1900 Princeton-Yale baseball game