In this composite character, the body of a cart is combined with three counting rods (the numeral three). The numeral indicates the relative size of the cart. Hence, Mahadevan's sign number 1248 is an ideograph for a large cart.
Illustrative Text References:
Mohenjo-daro: Seal: M-1135 a: Sayid Ghulam Mustafa Shah and Asko Parpola, 1991: Corpus of Indus Seals and Inscriptions: Volume 2: Page 125: Collections in Pakistan: Suomalainen Tiedeakatemia.
Mohenjo-daro: Seal: M-1794 a: Asko Parpola, B. M. Pande, and Petteri Koskikallio, 2010: Corpus of Indus Seals and Inscriptions: Volume 3,1: Page 52: New material, untraced objects, and collections outside India and Pakistan: Suomalainen Tiedeakatemia.
Comments:
Each of the sample texts gives us a dimension for a large cart of six Indus units.
The load referred to in inscription M-1794 has two lengths of matting side by side. Some of the children's toys were rectangular shaped carts. If we assume that the body of a the cart was rectangular in shape, then, the matting may have been fitted in the manner shown on the right.
It then follows that the length of the cart body referred to in M-1794 may have been six Indus units, and the width may have been four indus units.
Image Credits:
Indus Script Sign Number 1248: List of Sign Variants: Iravatham Mahadevan, 1977: The Indus Script: Texts, Concordance and Tables: The Director General Archaeological Survey of India.
Matting Pattern: Lynn Fawcett, 2017.