Only arguing for the sake of it. Bored. But, there's only 13 seatposts that weigh less than 150g. So you can't really really say "any lightweight seatpost" - more like, carefully handpicked ultralightweight seatpost. There's only six headstems that weigh less than 100g too.

AX-Lightness Europa
AX-Lightness Daedalus
New Ultimate
USE Alien Carbon
USE Alien Aluminium
Bold Precision
Heylight HS II Superleicht
Alpha Q Pro Lite
Extralite The Post UL
Felt SM-1
USE Alien Cyclops Carbon
Thomson Masterpiece
Easton EC90