How To Get To The Crows Nest

I have been fuming and having steam coming out of my ears and for the life of me, I have yet to find the means by which the lookout crews got up into the Crows Nest. I have been thinking that there was a ladder inside, but It got to be too thin. I also thought of the rigging on both sides, but they end to far up.
Anybody that are gurus please help me in this dilemma.
Private Clark Morningstar
7th Illinois Volunteer Infantry
Union Army
A tight fit, but quite accessable. Compare the size of the sailors to the width of the mast.

Dear Guys,

Thanks for your help, both of you. I did not realize that the mast was that big around! I am building a model, but what I am using will make it's construction difficult.
Thanks again,
Private Morningstar