I used to do something similar, but now eyes are not good enough. I found Lisa Bongean's method and it works great for me; I've used it for many different weights.
https://www.youtube.com/watch?v=KNJJBnluGJs
Not long before she passed, my MIL was no longer waking up. Her daughter and I were sitting with her one day, and Ma brought her thumb and forefinger almost to her mouth, then put them next to the thumb and forefinger of her other hand. Betty wondered what on earth Ma was doing. I told Betty that, in her mind, Ma was threading a needle, just as she had done thousands of times.