In the age before telegrams, telephones or e-mail, letters were the “ligaments” that bound society together, the only means of conducting “conversations” between parted, far-flung friends and associates.

As historical documents, they were also remarkably durable.

Through April 2, about seven dozen of the Folger Shakespeare Library’s abundant trove of manuscript and early printed letters are on display at the library as part of the exhibit “Letterwriting in Renaissance England.”

The exhibit explores the evolution and use of the nearly extinct form of communication, from its burgeoning popularity in the 16th century through to its more formalized entrée into society with the establishment of the United Kingdom’s first national postal service in the early 17th century and beyond.

Divided into four sections — writing letters, sending letters, reading letters and keeping and copying letters — the exhibit includes a variety of genres ranging from domestic to diplomatic to romantic missives.

Among the curiosities included are the first letterwriting manual published in English, recipes for invisible ink (to protect against unwanted interception by prying eyes), and a nearly 400-year-old love letter folded into a tiny packet and sealed with wax and embroidery floss.

By all accounts, Renaissance letterwriting was a complicated endeavor, wrought with myriad and exhaustive rules for its execution, and even uncertainty, should the missive be lost or stolen en route.

For instance, leaving “excessive white space” between the letter’s conclusion and the signature “was a way of showing greater deference,” says exhibit co-curator Heather Wolfe, noting that “paper was a very expensive commodity in the period.” Letters from prodigal sons to their fathers, a relatively common genre, would often sport a subscription toward the bottom of the page. In contrast, Queen Elizabeth I’s John Hancock flourish is placed directly under the text of one piece of her diplomatic correspondence with Spain’s Philip II.

That roughly one-fourth of 16th-century correspondence was penned by secretaries or other third parties further complicated communication. Indeed, the second Earl of Essex, Robert Devereux, found himself in hot water with his mother after she received an insulting letter bearing his name — no doubt penned by a mischievous secretary. Given the quantity of missives he was forced to sign, the chastised son explained in another letter to her, “I might signe some such ere [before] I knew whatt yt was.”

The woes of one former secretary — the English poet John Donne — come to life in a collection of his “marriage letters.” In them, Donne, whose revelation to his father-in-law of his secret wedding to Anne More left him jailed, unemployed and cut off from his wife, pleads his case in neat, perfectly ruled lines that belie any personal state of turmoil.

Meanwhile, a passel of rare love letters, which due to their personal nature were less likely to survive, offers a glimpse into the universality of affairs of the heart across time. In one, a woman worries why her lover’s letters have been so infrequent. In another, a woman confesses to her beloved — a cousin, no less — that she has revealed their affair to a family friend. She then signs the letter by intertwining their first initials in her signature much like any modern-day, mooning co-ed.

But perhaps the most intriguing aspect of the exhibit lies in the writing itself as it plays out upon the smudged and often tattered pages. There is the double-spaced, slanted hand of James I in his “secret letters” to a jailed and disgraced former favorite; the furtive, crowded italics of Oliver Cromwell’s sister; and even the Chinese-like characters of one Englishman with woefully inadequate penmanship.

As technology has advanced, the art of letterwriting has disappeared quicker than a designer wedding gown at a Filene’s Basement sale — a point not lost on the exhibit’s curators. Will our hastily pecked (and often just as hastily deleted) BlackBerried messages survive for posterity? It’s unlikely.

“Something like this couldn’t be done for us,” Wolfe concedes.

But one thing’s for sure, even if it could, the penmanship wouldn’t be nearly as interesting.