Put StartSystem=>true as an argument in the function mixedVolume to tell the method to use polyhedral homotopies. Polyhedral homotopies solve a system with the same Newton polytopes as the original system and with random complex coefficients. This random coefficient system can serve as a start system to solve the original input system.
The object StartSystem is a symbol.
The source of this document is in /build/reproducible-path/macaulay2-1.25.05+ds/M2/Macaulay2/packages/PHCpack/PHCpackDoc.m2:695:0.