This paper introduces the reader to Meinong's work on the metaphysics of magnitudes and measurement in his Über die Bedeutung des Weber'schen Gesetzes. According to Russell himself, who wrote a review of Meinong's work on Weber's law for Mind, Meinong's theory of magnitudes deeply influenced Russell's theory of quantities in the Principles of Mathematics. The first and longest part of the paper discusses Meinong's analysis of magnitudes. According to Meinong, we must distinguish between divisible and indivisible magnitudes. He argues that relations of distance, or dissimilarity, are indivisible magnitudes that coincide with divisible magnitudes called "stretches". The second part of the paper is concerned with Meinong's account of measurement as a comparison of parts. According to Meinong, since measuring consists in comparing parts only divisible magnitudes are directly measurable. Indivisible magnitudes can only be measured indirectly, by measuring the divisible stretches that coincide with them.