In 2010, Michael Hartl proposed to use the Greek letter tau to represent the circle constant: τ = 2 π. He offered several reasons for the choice of constant, primarily that it allows fractions of a turn to be expressed more directly: for instance, a ⁠ 3 / 4 ⁠ turn would be represented as ⁠ 3 τ / 4 ⁠ rad instead of ⁠ 3 π / 2 ⁠ rad. As for the choice of notation, he offered two reasons. First, τ is the number of radians in one turn, and both τ and turn begin with a / t / sound. Second, τ visually resembles π, whose association with the circle constant is unavoidable. Hartl's Tau Manifesto gives many examples of formulas that are asserted to be clearer where τ is used instead of π. For example, Hartl asserts that replacing Euler's identity e = −1 by e = 1 (which Hartl also calls "Euler's identity") is more fundamental and meaningful.