JOHANNESBURG: The power of ideas nourished Nelson Mandela during his confinement on Robben Island, but even this visionary might not have imagined the surreal scene planned for this month at the outpost where he spent 18 of 27 years as a prisoner of apartheid.

Wind speed and direction permitting, a man in a harness will strap himself to 200 big balloons filled with helium, float off the island beneath a bulging latex column of color, and drift to the shores of Cape Town for a charitable cause.

There are a few things he wants to avoid: an international airport, a major harbor, a nuclear power station, and the odd shark in the waters below.

“Apart from all those hazards, there’s nothing to worry about,” said Matt Silver-Vallance, a South African-born manager at a medical device company who will pilot the whimsical craft.

Civil aviation authorities say they are satisfied with safeguards for what should be a lazy meander in the breeze rather than an edge-of-your-seat stunt.

The goal of the trip is to raise $1 million to help build a children’s hospital named after 94-year-old Mandela, who became South Africa’s first black president in democratic elections in 1994 after negotiating an end to white racist rule.

Mandela was admitted last week to a Pretoria hospital because of a recurrence of pneumonia, prompting expressions of concern from South Africans and people around the world. On Monday, the office of President Jacob Zuma said family members visited Mandela at the hospital.

“It refocuses everybody on his legacy,” Silver-Vallance, who lives in Britain, said Tuesday of Mandela’s illness. The guardians of Robben Island, a somber site, concluded that the cluster balloon flight, while quirky, was consistent with the spirit of daring and altruism that Mandela personified in the struggle against apartheid.