I see the image on the page you referenced at 140px in width (width of the caption background) with an image width of 129px on the page you referenced.
What I might suggest, if you are going to insert an image at a size other than the predefined thumbnail, medium, large, or full-size, that you use the "insert from URL". What you would do is find the image in the media library, get the URL of that image and then use the insert from URL function. Once you have inserted the image, you can then click on the text tab and if you want a specific width for the image, remove the "height" part and then adjust the width as desired. Same if you wanted to control the height, you would then delete the "width" part. With only one size declared in the code, the proportions of the image will be preserved.
Here is an example where I tested this in one of my test blogs in Academica.
<img class="alignright" alt="" src="http://allhatnocattle.files.wordpress.com/2013/04/island-cabins-on-easter-island.jpg" width="300" />
If after inserting an image that you want to size differently, you see something like
after the image URL, delete that so that the image URL ends in the extension (.jpg, .png, .gif) as in my example code above.
Another way you can change the size of an already inserted image is to click on the image in the post/page editor, click on the edit image icon at top right of the image and then either adjust by percentages, or click on the advanced tab and enter a height or width (whichever you wish to change) and delete the other value. As an example, you want to set the width, so you enter the desired value in the width field and then delete the value in the height field and update the image.