 They date between the 15th and 20th Centuries, and represent a broad range of countries and languages.A list of known authors of letters in the collection

Napoleon,
Elizabeth I,
John Donne,
Charlotte Brontë,
Ludwig van Beethoven,
Albert Einstein,
Isaac Newton,
Frederick the Great,
Ernest Hemingway,
Charles Darwin,
Lewis Carroll,
Voltaire,
Alexander Pushkin,
Claude Monet,
Winston Churchill (aged 16),
Mahatma Gandhi,
Daniel Defoe,
Tchaikovsky,
Dostoevsky,
Ezra Pound,
Garcia Lorca,
Oliver Cromwell,
T. S. Eliot,
Lord Byron,
Sigmund Freud,
Charles Dickens,
Peter the Great,
John Calvin,
William Bligh,
Oscar Wilde,
Joséphine de Beauharnais.Joseph Addison,
Henri Alban-Fournier,
Bettina von Arnim,
W. H. Auden,
Honoré de Balzac,
Charles Baudelaire,
Pierre Beaumarchais,
Jorge Luis Borges,
James Boswell,
Johann Jakob Breitinger,
Bertholt Brecht,
André Breton,
Charlotte Brontë,
Patrick Brontë,
Elizabeth Barrett Browning,
Robert Browning,
Fanny Burney,
Robert Burns,
Lord Byron,
Lewis Carroll,
Giacomo Casanova,
Louis-Ferdinand Céline,
Nicolas Chamfort,
Anton Chekhov,
Joseph Chénier,
Philip Stanhope, 4th Earl of Chesterfield,
Paul Claudel,
Matthias Claudius,
Samuel Clemens (Mark Twain),
Samuel Taylor Coleridge,
Sir Arthur Conan Doyle,
William Congreve,
Joseph Conrad,
Édouard Corbière,
Marquis de Custine,
Thomas de Quincey,
Daniel Defoe,
Charles Dickens,
John Donne,
Dostoevsky,
Joseph Freiherr von Eichendorff,
George Eliot (Mary Ann Evans),
T. S. Eliot,
John Evelyn,
Edward Gibbon,
Johann Wilhelm Ludwig Gleim,
William Godwin,
Johann Wolfgang von Goethe,
Carlo Goldoni,
Oliver Goldsmith,
Johann Joseph von Görres,
Thomas Gray,
Graham Greene,
Franz Grillparzer,
Jacob Grimm,
Wilhelm Grimm,
Francesco Guicciardini,
William Hazlitt,
Johann Peter Hebel,
Heinrich Heine,
Ernest Hemingway,
Johann Gottfried Herder,
Henriette Herz,
E. T. A. Hoffmann,
Hugo von Hofmannsthal,
Joris-Karl Huysmans,
Washington Irving,
Henry James,
Francis Jammes,
Samuel Johnson,
James Joyce,
Franz Kafka,
Gottfried Keller,
Rudyard Kipling,
Heinrich von Kleist, 
Friedrich Gottlieb Klopstock, 
Jean de La Fontaine, 
Jules Laforgue, 
Walter Savage Landor, 
Valery Larbaud, 
Johann Kaspar Lavater, 
Nikolaus Lenau, 
Giacomo Leopardi, 
Mikhail Lermontov, 
Gotthold Ephraim Lessing, 
Friedrich, Freiherr von Logau, 
Jack London, 
Garcia Lorca,
François de Malherbe, 
James Macpherson, 
André Malraux, 
Thomas Mann, 
Alessandro Manzoni, 
Francois de Maucroix,
Guy de Maupassant,
Metastasio,
Conrad Ferdinand Meyer,
Henry Miller,
Eduard Mörike,
Pablo Neruda,
Gérard de Nerval,
Johann Nestroy,
Pierre Nicole,
Novalis,
Seán O'Casey,
Boris Pasternak,
Leo Perutz,
August von Platen-Hallermünde,
Ezra Pound,
Marcel Proust,
Jeanne Clemence Proust,
Alexander Pushkin,
Wilhelm Raabe,
Francesco Redi,
Samuel Richardson,
Jean Paul Friedrich Richter,
Rainer Maria Rilke,
Arthur Rimbaud,
Antoine de Rivarol,
Ludwig Robert,
Joseph Roth,
Saint-John Perse,
George Sand,
Friedrich Schiller,
Karl Wilhelm Friedrich Schlegel,
Johanna Schopenhauer,
Johann Gottfried Seume,
Marie de Rabutin-Chantal, Marquise de Sévigné,
Percy Bysshe Shelley,
Georges Simenon,
Tobias Smollett,
Sir Richard Steele,
Anne Louise Germaine de Staël,
Stendhal,
Laurence Sterne,
Christian zu Stolberg-Stolberg,
Theodor Storm,
August Strindberg,
Madame Swetchine,
Algernon Charles Swinburne,
Jonathan Swift,
John Millington Synge,
Torquato Tasso,
William Makepeace Thackeray,
Gerhard Tersteegen,
Dylan Thomas,
J. R. R. Tolkien,
Ludwig Tieck,
Leo Tolstoy,
Friedrich Torberg,
Ivan Turgenev,
Georg Trakl,
Paul Valéry,
Paul Verlaine,
Horace Walpole, 4th Earl of Orford,
Evelyn Waugh,
Franz Werfel,
Christoph Martin Wieland,
Oscar Wilde,
Virginia Woolf,
Dorothy Wordsworth,
William Wordsworth,
W. B. Yeats.