N O N E
After a long morning of standing in the dark making some very long exposures on film.
At one time I actually came very close to reproducing this in the darkroom.... Maybe I'll try that again.
Hasselblad 500 C/M
Zeiss 150mm CF
Lee 10 stop ND
Lee .3 & .6 hard edge ND grads
Tmax developer 1:4 (probably around 8-11 minutes)