Books and Lemon sketches, and Measuring

A few more sketches today with the conte pencil, and some nupastel for color on light brown paper.

I wanted to try a method for measuring the set up as I draw.   The usual way taught is to use a pencil or paint brush handle to sight your measurement of the subject, and then keep your finger on that spot, and transfer that distance to your drawing.  But, I always seem to have trouble doing that.   It's not very accurate.  My arm wobbles, and makes it hard to find a spot and keep it marked with my finger, and then laying the pencil flat to the paper while keeping my place with my finger just never works out for me. And then, if  I've measure the lemon in the set up, and figured out that the books width is 3 1/2 lemons worth, trying to keep that mark on my pencil and sight out 3 equal paces with it on my paper is always trouble.    What am I doing wrong?  Maybe it takes more practice??   I don't know, but I thought to make a thin ruler out of a peice of stiff paper. (I first tried a regular ruler, but it was too wide, and didn't have marks on both edges.)    It's easier to see where the marks on the ruler land on the set up, and easier to transfer to my paper.  No need to keep my finger in place to mark a spot.  It works as long as you want the drawing to be the same size as  your measurement. (although, you could add the same amount to each measurement to make your drawing bigger... Like, if something appears to be one inch, you could add 1/2 again, and transfer a measurement of 1 1/2 inches on your drawing, or a 1/4 inch with half added would be 3/8,  Or double each measurement for an even larger drawing )   I'll try this for a while and see how it works for me.   This cup always give me trouble though, no matter what I do.  It always comes out a bit wonky.  The ruler helped with checking distances of all the angles and edges of the books though.