Against the Professors, Books I-VI of Against the Learned Section 103

καὶ μὴν κοινῶς τῶν συμφώνων πάλιν τὰ μὲν φύσει δασέα λέγουσι τὰδὲ ψιλά, καὶ δασέα μὲν θ φχ, ψιλὰ δέ κ π τ· μόνον δέ φασι τὸ ρ ἐπιδέχεσθαι ἑκάτερον, δασύτητα καὶ ψιλότητα. λέγουσι δέ τινα τῶν συμφώνων καὶ διπλᾶ, καθάπερ τὸ ζ ξ ψ· συνεστηκέναι γάρ φασι τὸ μέν ζ ἐκ τοῦ σ καὶ δ, τὸ δέ ξ ἐκ τοῦ κ καὶ σ, τὸ δέ ψ ἐκ τοῦ π καὶ σ.

Again, among the consonants generally, some are said to be naturally aspirated and others unaspirated. The aspirates are θ, φ, χ, and the unaspirated letters κ, π, τ. They say that ρ alone admits both aspiration and lack of aspiration. They also call certain consonants double, such as ζ, ξ, ψ. For they say that ζ is constituted from σ and δ, ξ from κ and σ, and ψ from π and σ.

Ils disent encore que, parmi les consonnes en général, certaines sont aspirées par nature et d’autres non aspirées. Les aspirées sont θ, φ, χ, les non aspirées κ, π, τ. Seul ρ, disent-ils, reçoit les deux propriétés, aspiration et absence d’aspiration. Ils appellent aussi certaines consonnes doubles, telles ζ, ξ, ψ. Ils affirment que ζ est composé de σ et δ, ξ de κ et σ, et ψ de π et σ.