Whose will, in its early versions, called for the founding of a secret society with the aim of extending British rule throughout the world, especially in the Holy Land, South America, Africa, the Euphrates valley, and the Pacific Islands, with the ultimate return of the United States to the British Empire?

Cecil John Rhodes. Source

Very good, Mozart!

From Wikipedia -

Although Rhodes remained a leading figure in the politics of southern Africa, especially during the Second Boer War, he was dogged by ill health throughout his relatively short life.

In his will, he left his money for the establishment of a secret society that would enable Britain to rule the entire productive world. The exact words are as follows:

To and for the establishment, promotion and development of a Secret Society, the true aim and object whereof shall be for the extension of British rule throughout the world, the perfecting of a system of emigration from the United Kingdom, and of colonisation by British subjects of all lands where the means of livelihood are attainable by energy, labour and enterprise, and especially the occupation by British settlers of the entire Continent of Africa, the Holy Land, the Valley of the Euphrates, the Islands of Cyprus and Candia, the whole of South America, the Islands of the Pacific not heretofore possessed by Great Britain, the whole of the Malay Archipelago, the seaboard of China and Japan, the ultimate recovery of the United States of America as an integral part of the British Empire, the inauguration of a system of Colonial representation in the Imperial Parliament which may tend to weld together the disjointed members of the Empire and, finally, the foundation of so great a Power as to render wars impossible, and promote the best interests of humanity.

As a result of his will, the Rhodes Scholarships, which enable foreign nationals to study at the University of Oxford, came into being. Rhodes died in 1902, and was considered at the time one of the wealthiest men in the world.

Interesting, DG, and quite the anglophile.
I hadn't realized that is where "Rhodes scholar" originated.

We had a Rhodes scholar/US President question in the last Trivia contest, and we discussed the only Presidents who were even eligible. I assumed that the scholarship started later, and that because of that, thought that Kennedy would have been the first to be the right age. In the end, we went with Clinton, since we knew that he was a Rhodes scholar, and thought that he was the only one. (The question was, "Who was the first US President to be a Rhodes scholar?") When I checked to find out about it at home, I was surprised to find out that every President after Hoover was college age when the scholarship was first awarded.