A while back, so the story goes, a group of farmers here in the Orange Free State took up a collection and sent the money to a university with the request that it "prove, once and for all, that the world is really flat."

The Afrikaner of this central province prides himself on being more conservative, more shrewd and admirably tougher than his up-country kin in the Transvaal, and he is conscious that he comes from a place where Afrikaners' history has deep roots. In 1854, the Boers of the Orange Free State received their independence from the British in this provincial capital, which today is the seat of South Africa's highest appellate court.

What better place then, the government must have reckoned, to send a black woman who, for 16 years, despite being banned, detained and harassed by police, has remained at the center of the anti-apartheid force in the black community?

What better place, indeed, to send Winnie Mandela, 43, almost always described as the wife of 60-year-old Nelson Mandela, a former executive of the banned African National Congress who is serving a life sentence on Robben Island for his anti-government activities.

But Winnie Mandela, statuesque and outspoken, definitely has her own laurels, earned from unflinching opposition to the repression of black aspirations in South Africa. According to one observer, she is regarded as sort of a "mother figure" among the moderate blacks and has been accepted by most, though not all, radical blacks.

She helped found the powerful, now banned, Black Parents' Association in the wake of the 1976 riots in the Johannesburg township of Soweto. The government has produced statements, from a student detained under the Terrorism Act, alleging that Mandela had an active part in encouraging the students to confronting the police.

Believing her to be one of the motors behind the unrest, the government acted against her five months before they detained the rest of Soweto's leadership last October.

The minister of police, prisons and justice, Jimmy Kruger, unsheathed the weapon meant for people unlikely to wither on the vine despite the constant shadow of the security police.

Mandela was uprotted - "banished" from her home in Soweto where she har lived most of her adult life to a three-room concrete shell, without plumbing or electricity, in the black area of the Orange Free State village of Brandfort. It is 200 miles from Soweto and 36 miles northeast of Bloemfontein - a move that is asking to force resettling a well-heeled Washingtonian to a log cabin in the Ozark mountains.

As a banished person, Mandela is under a host of restrictions designed to isolate her from the other human beings and to demoralize her. She must be in her home from dusk to dawn and on weekends. She lives with her daughter Zinzi, 16, but cannot be in the presence of more than one other person at a time and may not receive visitors, even relatives, except by special permission of the local magistrate.

"It is literally a living grave," she said. "One loses touch. I keep my sanity by reading."

Brandfort's security police, unaccustomed to handling a banished person, especially someone as well-known as Mandela, went about their task with the energetic zeal of the uninitiated.

"My house was an annex of the police station - it was an operational area," Mandela said. The sergeant, Gert Prinsloo, "would come into my house at any time and even look under the bed."

The vigilance produced five charges against Mandela for allegedly violating the terms of her banishment by participating in a "social gathering" and by receiving visitors without permission. Her trial on the charges, for which she could get a maximum of 15 years in prison, was held in Bloemfontein regional court.

In Criminal Courtroom, D, C.P.J. Steytler, the tall, thin and bespectacled magistrate, seldom smiled during the non-jury proceedings. Neither did the mostly young blacks, who filled the "white" and "black" sides of the public gallery, the aisles and the entrances.

Facing magistrate was George Bizos, a portly Johannesburg lawyer who has defended Mandela since 1971, when she was charged with resisting arrest by smacking a white policeman who walked into her bedroom. (She was acquitted). Bizos was also an assistant counsel to the family of Steve Biko at the inquest into the death in custody of the black consciousness leader.

Assisting Bizos as junior counsel here was boyish-looking Clifford Mailer, a first cousin to American author Norman Maller.

A contingent of Bloemfontein security police sat opposite the witness stand. Among them was Prinsloo, resembling a Calvinist minister who might have preached to Nathaniel Hawthorne's New Englanders.

Amid the police sat Neil Botha, the young, blond prosecutor whose discomfitted air made it plain that his heart was not in his task. According to reliable sources, Botha had recommended not prosecuting Mandela, but the police then appealed to the provincial attorney general, who gave the go-ahead for the prosecution.

Botha did pose his questions earnestly. When he cross-examined Mandela he wanted such information as, "Did you or did you not discuss the price of a chicken with a post office employee in Mrs. Dlas' house? Did you speak to your sister when she was in your home?"

In his summation, Botha quoted at length South African judicial decisions defining a "social gathering." A discussion about the price of a chicken could legally be construed as a social gathering because it is different for example, from standing in a bus line, he said.

Bizos argued that Mandela did not take part in the alleged conversations and that she believed in good faith that the police had given her informal permission to receive her visitors. Testimony has been completed and the magistrate set Feb. 9 for judgment.

If Mandela is sent to jail, it will not be the first stay for the onetime social worker in Soweto. She was detained at length twice before and was under banning orders in her Soweto home for all but nine months of the past 16 years. In 1970, she was charged under the Terrorism Act, but acquitted.

Mandela has irrespressibly thumbed her nose at the government throughout the years. She once came into Bloemfontein's courtroom dressed in green, gold and black, the colors of the banned African National Congress.

In 1975, during a respite in her banning orders, she happened to spot Jimmy Kruger taking his luggage out of his car at Durban airport. "How do you do, Mr. Kruger?" she asked. "When are you going to release my husband?" Kruger later told a reporter the meeting was "an embarrassment."

During the final two days of her trial last week, Mandela spent out-of-court playing with her 7-month-old grandaughter. Asked what she would say if she could speak in public, she replied:

"There is nothing more to be said. The people know. We are heading for grimmer times ahead. The Afrikaner is going more and more into the laager. There is going to be a racial war."

Although living in the isolation of the Orange Free State was meant to be a punishment, Mandela says she appreciates living so close to Bloemfontein - because there is something in its history that an official guide probably would not tell.

In 1912, blacks from all over South Africa gathered here to from the most durable balck nationalist organizations, the now banned African National Congress. "I feel honored to be brought home," said Mandela outside the Bloemfontein regional court.

At the close of her trial, the black audience joined her in giving the clenched-fist black power salute. At her home in Brandfort, passers-by do the same.

"Winnie won't change," said one friend, "but Brandfort will never be the same."