Who said "To stand upright, you need something inside."?

The Spartans (8th–4th century BC). Source: Plutarch, Sayings of Spartans, Anonymous 50 (234f).

What is the original Greek?

νὴ τὼ σιώ εἶπεν ἔνδον τι εἶναι δεῖ. Translated from the original Greek by Spartan Surfers.

To stand upright, you need something inside.

The Spartans, Plutarch, Sayings of Spartans, Anonymous 50 (234f)

The source

"To stand upright, you need something inside." The Spartans said it in Plutarch, Sayings of Spartans, Anonymous 50 (234f). Translated from the original Greek by Spartan Surfers.

"νὴ τὼ σιώ εἶπεν ἔνδον τι εἶναι δεῖ."

Original Greek, Plutarch, Sayings of Spartans, Anonymous 50 (234f). Greek: Bernardakis 1889 (Teubner) via Perseus.

Who said it

The Spartans (8th–4th century BC). Laconic sayings from Lycurgus, Leonidas, Dienekes and the mothers of Sparta, recorded by Herodotus and Plutarch.

Questions

Who said "To stand upright, you need something inside."?: The Spartans (8th–4th century BC). Source: Plutarch, Sayings of Spartans, Anonymous 50 (234f).
What is the original Greek?: νὴ τὼ σιώ εἶπεν ἔνδον τι εἶναι δεῖ. Translated from the original Greek by Spartan Surfers.