This is such a simple adaptation that I had not even thought about adding it to the site until we used it in lab today. When counting how many (of anything) a student is measuring, a print student will often use tally marks. How is a student with visual impairment to accomplish this task? The system I use is simple. I have the student physically move one small object from one container to another each time he/she adds a unit (or measures a unit. I use gram weights Interlocking gram unit cubes, set of 1,000, but any small object would work (pennies, for instance). I would not recommend using marbles. As he/she measures, he will be able to gauge the total by how many of the counters are in the container to which they have been moved. The student should always move "counters" from left to right. so that he won't forget which way he is moving the counters.
An example from today's lab will make this adaptation more clear. One of my student's science projects required measuring the soda left in 2 bottles after a coke-mentos explosion. As he measured using a Savi Selph adapted beaker, he moved a gram weight from one container to another after each 100 mL was measured.