The romantic literati left not only their works, but also their love letters, which give an insight into their private lives. Think of John Keats and Fanny Brawne, James Joyce's letters to Nora, or the famous correspondence between the medieval abbess Héloise and her tutor Abelard.
Other less likely contenders showed their softer side, like this from Napoleon Bonaparte just before he married Josephine in 1796: "I wake filled with thoughts of you. Your portrait and the intoxicating evening which we spent yesterday have left my senses in turmoil. Sweet, incomparable Josephine, what a strange effect you have on my heart!"
Many of Shakespeare's plays rely on the safe, or unsafe, receipt of sweet words.
But the billet-doux is in danger of dying out, according to recent research. Less than 20 per cent of people have received a letter of affection over the course of the past year, and only 28 per cent have received one over the past five.
There is a clear generation divide. The majority of 16- to 34-year-olds have never written a love letter, while nearly all of their parents and grandparents have. Young people do not court that way.
But the love letter's decline may not be a sign of diminishing romantic feelings. Paper and pen have been exchanged for texts or email as the busy generation opts for instant communication. Type "romantic texts" into Google and, as well as analysis of love letters, up pop a number of websites suggesting mobile phone messages that fit into the number of characters available. One such suggestion reads: "If i died or went sumwhere far i'd write ur name on every star so everyone could look up n see u mean the world 2 me."
It might not seem as romantic as the ribbon-bound scroll, but Paula Hall, a Relate relationship counsellor, says it's not the means of communication, rather the sentiment that counts. "Emoticons might not be the same as rose petals, but it's the effort behind the communication that means more than anything. A three-page email is better than a scribbled note on the back of a fag packet."
Indeed, an email could be more meaningful than a handwritten letter, according to Hall.
"Lots of people will agonise over an email: they can keep reflecting on it and go back and make changes, which you cannot do with a handwritten piece."
The authors of Four Letter Word: New Love Letters (Chatto) disagree. They believe writing love letters is an art to be preserved. Worried by the decline, Joshua Knelman and Rosalind Porter asked 40 famous authors, from Margaret Atwood to Hari Kunzru, to write fiction celebrating the force of the love letter (modern technology is represented, though, with Chimamanda Ngozi Adichie's text message love letter).
And the rarity of handwritten love letters may give the few that are written added significance. Let us hope, however, that no one would now damn them with the faint praise offered by the French poet Henri de Régnier: "It is well to write love letters. There are certain things for which it is not easy to ask your mistress face to face, like money, for instance."