Thomas Fuller, familiarly known as the Virginia Calculator, was a native of Africa. At the age of fourteen he was stolen, and sold into slavery in Virginia, where he found himself the property of a planter residing about four miles from Alexandria. He did not understand the art of reading or writing, but by a marvellous faculty was able to perform the most difficult calculations.

Dr. Benjamin Rush of Philadelphia, Penn., in a letter addressed to a gentleman residing in Manchester, Eng., says that hearing of the phenomenal mathematical powers of “Negro Tom,” he, in company with other gentlemen passing through Virginia, sent for him. One of the gentlemen asked him how many seconds a man of seventy years, some odd months, weeks, and days, had lived, he gave the exact number in a minute and a half. The gentleman took a pen, and after some figuring told Tom he must be mistaken, as the number was too great. “‘Top, massa!” exclaimed Tom, “you hab left out de leap-years!” And sure enough, on including the leap-years in the calculation, the number given by Tom was correct.

“He was visited by William Hartshorn and Samuel Coates,” says Mr. Needles, “of this city (Philadelphia), and gave correct answers to all their questions such as, How many seconds there are in a year and a half? In two minutes he answered 47,304,000. How many seconds in seventy years, seventeen days, twelve hours? In one minute and a half, 2,110,500,800.”

That he was a prodigy, no one will question. He was the wonder of the age. The following appeared in several newspapers at the time of his death.

Present day thinking is that Fuller learned to calculate in Africa before he was brought to the United States as a slave. Supporting evidence for this comes from a passage written by Thomas Clarkson in 1788 describing the purchase of African slaves:

It is astonishing with what facility the African brokers reckon up the exchange of European goods for slaves. One of these brokers has ten slaves to sell , and for each of these he demands ten different articles. He reduces them immediately by the head to bars, coppers, ounces… and immediately strikes the balance. The European, on the other hand, takes his pen, and with great deliberation, and with all the advantage of arithmetic and letters, begin to estimate also. He is so unfortunate, as to make a mistake: but he no sooner errs, than he is detected by this man of inferior capacity, whom he can neither deceive in the name or quality of his goods, nor in the balance of his account.

Despite Fuller’s calculating abilities he was never taught to read or write and again this is evidence that he did not learn to calculate while in the United States. When someone who had witnessed his calculating abilities remarked that it was a pity he had not been educated, Fuller replied: ‘It is best I got no learning; for many learned men be great fools.’

Source:http://www.freedmenscemetery.org/resources/families/documents/fuller.shtml

Source:  Thomas Fuller African ”slave” And Mathematician..