On 10 May, 1819, John Quincy Adams received in the mail a parcel he had been expecting. He was living in Washington, D. C., and was serving as Secretary of State to President James Monroe. What Adams wrote in his diary about the contents of that parcel tells us something about him and about how to keep in continuity with the classical past.

Before looking into that parcel and reading Adams’s diary entry about it, a few points are in order. In 1819, Adams’s father, John Adams, was still living; eighteen years earlier he had finished his one term as the young republic’s second president. In 1824, the younger Adams would become the country’s sixth president, likewise serving one term.

Also, when writing in his diary about the books he got in the mail, Adams referred to an ancient custom that is now obsolete and obscure. Such was the reverence ancient Romans held for the Aeneid, the epic poem by Vergil (or Virgil, if one prefers), that they would open it at random and alight on a line and use it to make a decision or determine a course of action. Called sors Vergiliana, it was a kind of combination lottery and horoscope, and in that Latin word sors lurks the root of our word sorcery.

The books Adams received came from Wells and Lilly, book publishers in Boston. They had borrowed his copy of an eighteenth-century scholarly edition of the works of Cicero in order to produce their own edition. Also in the parcel that Adams unwrapped was an edition of the works of Tacitus. Adams was a lover of books but also a busy man, and he wrote about the tension caused within him by those conflicting claims on his time.

“I cannot indulge myself in the luxury of giving two hours a day to these writers,” he told his diary, “but to live without having a Cicero or a Tacitus at hand seems to me as if it was a privation of one of my limbs.” Living without books by Cicero or Tacitus seeming like losing a limb has become an oft-quoted line from Adams’s diaries.

Still, he could not bring himself to set the books aside just yet. “I opened a volume of the Tacitus,” he wrote, “and by a kind of sors Tacitina, fell upon the passage, ‘Fidem, libertatem, amicitiam, praecipua humani bona, tu quidem eadem constantia retinebis’.” He had underscored the first three words, and David Waldstreicher, editor of the Library of America’s 2017 two-volume edition of Adams’s diaries, offered an English translation from 1839: “Good faith, independent spirit, constancy in friendship; the prime virtues of the human character which you must endeavour to retain unshaken.”

That sentence came from Book 1, Chapter 15, of Tacitus’ Histories and was part of advice given to a young senator by the ill-fated emperor Galba. It was customary for ancient historians to paraphrase or rearrange, if not outright make up, speeches by other ancient personages, and Tacitus noted that Galba spoke more or less along those lines. For the Adamses, however, the words mattered more than how they got on the page.

“More than thirty years ago,” Adams wrote, “my father selected the three emphatic words of this passage for a motto; and I have had them these 25 years as the motto upon my cypher seal.” With Adams opening Tacitus at random and hitting upon that line, with its strong family significance, it gives one pause as being rather spooky.

All the same, those three Latin words, abstract nouns, formed a bond not only between father and son, but also across the centuries back to ancient Rome itself. Fides, libertas, amicitia, faith, freedom, friendship: continuity of ideals from Galba and Tacitus to two Adamses.

On 12 May, 1780, John Adams wrote to his wife, Abigail, a letter that closed with words that have been quoted many times to sum up his practical approach to life. “I must study politics and war,” he told her, “that my sons may have liberty to study mathematics and philosophy.” In turn, he said, “my sons ought to study mathematics and philosophy, geography, natural history, naval architecture, navigation, commerce, and agriculture, in order to give their children a right to study painting, poetry, music, architecture, statuary, tapestry, and porcelain.”

Apparently slipping his mind were the times he encouraged his oldest son to study history. As Robert V. Remini put it in his biography of John Quincy Adams, John Adams had “advised him to read history so that he could be better equipped to recognize evil and treachery in the world.” Being able to spot evil and treachery was one reason Tacitus, a senator and provincial governor, had decided to write Roman history.

Only the first five Books of Tacitus’ Histories survive, but in his preface Tacitus explained that the work would recount the civil war that resulted after the suicide of the emperor Nero. Galba was a renowned and competent Roman general who claimed the imperial throne upon hearing of Nero’s death. Galba’s sterling reputation augured well for a return of good government and an end to what Michael Grant, in The Twelve Caesars (1975), called “melodramatic eccentrics of the Julio-Claudian type.”

Instead, Galba managed to prove politically inept at every turn. Six months into his reign nearly everyone had had enough, and an angry mob in Rome stabbed him to death. Tacitus, ever perceptive, witty, and concise, wryly observed, “Everyone agreed he was capable of being emperor, had he never reigned.”

Those astute words stand as an assessment of many political figures who have fallen short of expectations. Indeed, they could well apply to most one-term American presidents, the Adamses not least. Both Adamses were serious men, impatient and direct in dealing with anyone who seemed less serious in approaching what to an Adams were always serious matters of state. “He did not aim to please,” James Traub, a recent biographer of John Quincy Adams, has observed, “and he largely succeeded.”

As with other serious men in public life, duty called. Much as Adams wanted on that day in early May to re-read passages of his favorite classical authors, he had work to do. Timeless classics had to wait for modern times: “I was obliged,” Adams wrote, “immediately to lay aside my books, to ramble over the waste of daily newspapers.”