How to measure seatpost size

Get some glue, a shoelace and a ten pence piece.

Glue the ten pence piece onto the end of the shoe lace, lace this up on one of your trainers leaving the ten pence dragging on the floor behind you.

Go into Maplins and pick up a set of digital calipers, go over to the counter and say 'excuse me someone has dropped some cash here' (pointing at the ten pence).

When the cashier comes around to pick up the money kick him in the head and run out of the shop with the calipers.

lol

I'm crying now.