None of these people took the reading. The record of each shows the shape.
Alfred Russel Wallace (1823 to 1913)
Alfred Russel Wallace spent four years collecting in the Amazon and eight in the Malay Archipelago, where he gathered 125,660 specimens. He reached the theory of natural selection independently of Charles Darwin, and in 1889 he called his own book on it Darwinism. Twelve years of first work in new ground for others to build on, with the theory's name handed to another man, show the shape from outside.
Sources: en.wikipedia.org, gutenberg.org
Elzéard Bouffier (fiction)
In Jean Giono's The Man Who Planted Trees (1953), the shepherd Elzéard Bouffier plants trees for decades in a bare valley in the foothills of the Alps near Provence, officials take the new forest for a natural oddity, and the more than ten thousand people who later live there do not know whom they owe it to. Work done ahead of the people who will need it, kept up for decades and never traced to its maker, shows the shape from outside.
Source: en.wikipedia.org