With the development of articulated metal structures during the 19th century and the recognition of statical-indeterminacy, an era of intense interest in labour-saving extremum principles emerged. Outstanding among those principles is that of ‘least work’. It was discovered independently, principally by Menabrea, Castigliano, and Fränkel. This paper is concerned with the conceptual contrasts of their work, as being
highly instructive. Interesting personal relationships are necessarily included with Cremona’s judgment of Menabreand Castigliano following their notorious dispute within the Academy of the ‘Lincei’.