Because it [sic!] uses a figure of speech, an antithesis to oppose similar instruments, a crux (which he called stipes) several crux [sic: the plural is cruces]. Consider the context, and examine it carefully, you will understand it better.
if he is using a figure of speech, why would you think he is using crux to mean stipes, that is, the main post, exclusively? And why would you take it to mean that patibulum also meant stipes? Yes, he is using figures of speech to show that in the context (referring to those who do not fight their desires, but willingly give themselves fully to them, thereby "crucifying" themselves -- remember, Seneca was a Stoic) figurative nails (clavi), posts (stipitites), transverse beams (patibula), impaling stakes or the full frames (cruces) are the same as these people's desires (cupiditates)*. They do not necessarily mean that out in the real they are all one in the same! In fact, Seneca differentiates them as differing lethal instruments of suspension and torture out in the real world (DeConsolatione 20.3, Epistulae Morales 14.5, 101.10-14), as leolaia as demonstratively shown.
* I am using the nominative plural in each case.
Already this graffiti (sic! -- these graffiti [Pozzuoli and Vivat Crux]) proves nothing in the question of Jesus. Moreover, this element is strangely unknown (or ignored) by most scholars of the crucifixion. So it is certainly not evidence of weight. Moreover, this testimony could dated second century AD. If true, this testimony appears at the time found the first descriptions of the cross as we know it today (Barnabas, Lucien (sic), graffiti on Mount palatine, etc..)
The Pozzuoli is from about 100 CE; the Vivat Crux (found in Pompeii) 79 CE at the latest. Also found in Pompeii was an obscene graffito, IN CRVCE FIGARUS, meaning, "may you be fixed on/by the crux."
I can tell you right away scholars on this subject they ignore it almost completely. I know how contemporary scholars ignore, or worse, tend to negate the simple, obvious meaning of anaskolopizw through rationalizations. And there are some ancient, byzantine, and medieval scholars, even Julius Lipsius, who translated the greek anaskolopizw into the Latin in crucem agere, and/or vice-versa. Even Victorian scholars were not as bad as contemporary scholars.** Yet if anyone knows anything about the human body, one must use a support with a restrainer to keep the condemned person from hanging out from the crux, with the chance the nails might rip through the hands, wrists or even forearms, or let go of the wood. If such a device is not to be used, one had best use ropes.
Epistle of Barnabas: 80-120 CE.
Lucian of Samosata: 125-180 CE.
Alexamenos Graffito: about 200 CE.
Not exactly contemporary, except perhaps Barnabas. The others are later.
**Harry Thurston Peck, Dictionary of Classical Antiquities (1898), "Crux."
It was impossible that the whole weight of the body should rest upon the nails; hence there was a piece of wood projecting from the stipes on which the sufferer sat, or rather rode (Tertull. adv. Nat. i.12; cf. adv. Haer. i. 12 [sic - Iren. adv. Haer. ii.24]). The expression acuta si sedeam cruce, in the famous lines of Maceneas ap. Pliny [sic - Seneca] Ep. 101, probably refers to this support, and not, as lipsius thought, to impalement. when it was wanting, the body was probably sustained by ropes.
**William Smith, LLD, William Wayte, G. E. Marindin, Ed. A Dictionary of Greek and Roman Antiquities (1890), "Crux."
It was impossible that the whole weight of the body should rest upon the nails; hence there was a piece of wood projecting from the stipes on which the sufferer sat, or rather, rode (keras ep' w epoxountai oi stauroumenoi, Just. Mart. Dial. c. Tryph. 91; sedilis excessus, Tertull. Adv. Nat. 1.12; cf. Iren. adv. Haer. 1:12 [sic - adv. Haer. 2.24]. The expression acuta si sedeam cruce, in the famous lines of Maceneas ap. Sen. Ep. 101, probably refers to this support, and not, as Lipsius thought, to impalement (see Archd. Farrar in Dict. of the Bible, s.v. Cross). whwn it was wanting, the body was probably sustained by ropes: the combination of ropes with nails is mentioned by Pliny (fragmentum clavi a cruce and spartum e cruce as charms, H.N. 28.46) and Hilary ("colligantum funium vincula et adactorum clavorum vulnera," de Trin. 10).
Pliny Elder 23-79 CE. fragmentum clavi a cruce means fragment of a nail from a crux.
Hilary 300-368 CE
And even when the support was provided, in order to lift the condemned up with the patibulum, they had to use ropes anyway. What does in crucem tollere mean to you? It means "to lift up into the cross / onto the stake"
