.Mechanic Fourth
The fourth degree component is a quartic function, with its root curves.
The quartic, here silhouetted as the vertical line at center,

has two "independent", (my term) root curves, seen at left and right;

and one "dependent" root curve, the fork at center -- (resembling a parabola).
Another view shows the "real" quartic in profile,

descending from the upper left, reversing, and rising to the upper right.

Though the independent rootcurves are threads in the curtain, the quartic itself is not.

The dependent root curve pierces the curtain.
The independent root curves can, from a given angle make "eyes".

Here, with the addition of a frowning, or fishlike mouth,

they invoke a less human, I think less beautiful, Nefertiti's Curves.
Taken on a more mathematical level, they bear a resemblance to an eccentric hyperbola.

This can be seen in the figure above, in the first figure on the page, and, as well, in Nefertiti's Curves.

As these are quartic, (Nefertiti's were cubic), one can expect additional complexities.

For one thing, Nefertiti's hyperbolas were centered on their cubic.

Here they're off-center on the quartic, and likely involved with its free inflection point.