In existographies, Wassily Leontief (1906-1999) (CR:8) was German-born American economist noted for being one of the 1941 doctoral advisors for Paul Samuelson and for his 1953 lecture “Mathematics in Economics”, wherein he traces the origin of mathematical economics from Willard Gibbs to Irving Fisher to Edwin Wilson to Samuelson. [1]

Gibbs-based | Mathematical economics
In 1953, Leontief, in his “Mathematics in Economics”, stated the following summary:

“Fisher and Wilson were leading spirits in the organization—twenty-three years ago—of the international Econometric Society which now unites 2,500 economic statisticians and economists who claim the ability to speak—or at least to understand when spoken to—the ‘language of mathematics’ which Gibbs used with such compelling and poetic power.”

Leontief then commented how not every economist is in alignment with mathematical economics, of this sort, e.g. citing John Keynes as referring to it as "mere concoctions."

Leontief goes onto stitch this together, historically, with the general equilibrium theory of Leon Walras—and before him Daniel Bernoulli, Augustin Cournot, and E.J. Dupiut, in mathematical form—and after him in the work of Vilfredo Pareto, his contemporaries and successors.

Samuelson anecdote
In circa 1941, Samuelson, following his Harvard’s Society of Fellows intellectual sojourn (1937-1940), quickly wrote up his PhD dissertation, after which, as the story goes, when he completed his defense of his doctoral dissertation, one member of the committee, great economist Joseph Schumpeter, turned to Wassily and said, “did we pass?”; or specifically, as William Barnett, in co-editor association with Samuelson (2007): [2]

“It is widely reported that at the end of Samuelson’s dissertation defense at Harvard, the great economist Joseph Schumpeter turned to Nobel Laureate, Wassily Leontief, and asked, ‘Well, Wassily, have we passed?’”

The exact date of this defense needs to be tracked down, but whatever the case, most sources report that Samuelson received his PhD in 1941 from Harvard —though, to note, somehow, he had moved to MIT before finalizing his PhD (see below) (check). Samuelson’s thesis, according to Andrew W. Lo, modeled each person as an economic agent, and assumed that each individual acted so as to maximize a quantity called ‘expected utility’, a model with which he assumed should be able to predict their behavior in much the same way that physicists predict the behavior of physical objects.

Quotes | By
The following are quotes on Leontief:

“How long will researchers working in adjoining fields abstain from expressing concern about the splendid isolation within which ‘academic economics’ now finds itself.”
— Wassily Leontief (1982), “Letter to Science magazine” [3]

References
1. Leontief, Wassily. (1953). “Mathematics in Economics”, 27th Josiah Willard Gibbs Lecture, AMS, Baltimore Maryland, Dec 28; in: Bulletin of the American Mathematical Society, 60(3), May, 1954; in Essays in Economics: Theories and Theorizing, Volume 1 (pgs. 22-44). M.E. Sharpe, 1976.
2. Samuelson, Paul and Barnett, William A. (2007). Inside the Economist’s Mind: Conversations with Eminent Economists (§:Coeditor’s Preface: an Overview of the Objectives and Contents of the Volume, pgs. xi-). Wiley.
3. Hall, Charles and Klitgaard, Kent. (2011). Energy and the Wealth of Nations: Understanding the Biophysical Economy (pg. vii). Springer.

External links
● Wassily Leontief – Wikipedia.