Entry for challenge : Steampunk: Myths and Legends by CGTalk.

In Greek mythology, the centaurs (from Ancient Greek: Kéntauroi) are a race of creatures composed of part human and part horse. In early Attic vase-paintings, they are depicted with the torso of a human joined at the waist to the horse's withers, where the horse's neck would be.
The centaurs were usually said to have been born of Ixion and Nephele (the cloud made in the image of Hera).The whole story of Ixion is :

"Ixion was king of the Lapiths, the most ancient tribe of Thessaly, and a son of Ares or Antion or the notorious evildoer Phlegyas, whose name connotes "fiery".Ixion married Dia, a daughter of Deioneus and promised his father-in-law a valuable present. However, he did not pay the bride price, so Deioneus stole some of Ixion's horses in retaliation. Ixion concealed his resentment and invited his father-in-law to a feast at Larissa. When Deioneus arrived, Ixion pushed him into a bed of burning coals and wood.
Ixion went mad, defiled by his act; the neighboring princes were so offended by this act of treachery and violation of xenia that they refused to perform the rituals that would cleanse Ixion of his guilt.Thereafter, Ixion lived as an outlaw and shunned. By killing his father-in-law, Ixion was reckoned the first man guilty of kin-slaying in Greek mythology. That alone would warrant him a terrible punishment.
However, Zeus had pity on Ixion and brought him to Olympus and introduced him at the table of the gods. Instead of being grateful, Ixion grew lustful for Hera,Zeus's consort, a further violation of guest-host relations. Zeus found out about his intentions and made a cloud in the shape of Hera, which became known as Nephele, and tricked Ixion into coupling with it. From the union of Ixion and the false-Hera cloud came Centaurs..."

Here are some excerpts from Ancient Roman philosophers and mythographers' writings which may shed some light on this "unnatural birth" of centaurs :

Pseudo-Hyginus, Fabulae 62 (trans. Grant) (Roman mythographer C2nd A.D.) :
"Ixion, son of Leonteus, attempted to embrace Juno [Hera]. Juno, by Jove’s [Zeus'] instructions, substituted a Cloud (Nube), which Ixion believed to be the likeness of Juno. From this the Centauri were born."

Cicero, De Natura Deorum 3. 20 (trans. Rackham) (Roman rhetorician C1st B.C.) :
"A Nubes (Cloud) [Nephele] is fabled to have given birth to the Centauri."

These bring one's mind the "cloud" which was a fake form of Hera could resemble to the "steam technology" which would give birth , or in other words "energy to live" to centaurs in collaboration with the wisdom (knowledge of all kind of science) of Zeus to shape things.And Ixion might fell in love with this technology.
Actually,if we take a closer look to the logic of Lucretius, we may conclude that the birth of centaurs could indeed be the result of a bio-mechanical experiment:
"Lucretius in his 1st century BC philosophical poem On the Nature of Things denied the existence of centaurs based on their differing rate of growth. He states that at three years old horses are in the prime of their life while at three humans are still little more than babies, making hybrid animals impossible."
Lucretius was right on the lifespan and the rate of growth, but lacked the knowledge of the technology which would appear nearly 2 milenniums later which could make the centaurs appereance possible.Such a technology was already possible for Zeus.So he created Centaurs on top of Mount Pelion.