I have just finished reading Samuel Pepys: The Unequalled Self by Claire Tomalin, which was a hilarious and eye-opening book into the late 17th century. One of the things I found most interesting about the book was, however, how Tomalin described the discovery of the Diaries.
Pepys' Diaries ended up in the Bodleian Library in Oxford. In 1812 a Scottish historian, David Macpherson, included a few words from the Diary to illustrate the growth of the tea trade in Europe - Pepys had his first cup of tea and recorded the fact on September 1660, writing the words 'Cupp' and 'Tee' in longhand. Pepys actually wrote the first mention we have in English of anyone drinking a cup of tea.
What is most fascinating about this is how Macpherson found this one reference among six volumes of the Diary, how Macpherson managed to understand the Diary (it was written in code), and how Macpherson came to know to look at the Diary for information on the tea trade in the first place (it was relatively unknown and Pepys was far from a household name at the time).
His book, History of the European Commerce with India was noticed by chance by an Oxford scholar, George Neville, who was intrigued to know what else was in the Diaries - Pepys had after all lived through momentous times - the restoration of the monarchy, the last great plague epidemic, the Great Fire of London of 1666. He set an under-graduate on the task of breaking the code and transcribing the Diary. John Smith spent three years on this task, from the spring of 1819 until 6 April 1822, when he completed the transcription of Pepys' 3,102 pages on to 9,325 of his own, filling 54 notebooks.
Had Pepys not had that cup of tea, Macpherson not found it and wrote about it in his book, Neville been less curious about what else the contents might have held and Smith less intelligent, then the name Pepys might only be known to naval historians, and a very considerable part of what we know about how people lived in the second half of the 17th century would be unknown.
So it is very lucky he had that cup of tea.