True. It isn't literally present as that sentance in Understanding Media: The Extensions of Man (1964), but is a summarization. Amputation is mentioned 15 times and augmentation twice.

The concept that "every augmentation is an amputation" is best captured in Chapter 4, "THE GADGET LOVER: Narcissus as Narcosis." The chapter explains that any extension of ourselves is a form of "autoamputation" that numbs our senses.

Technology as "Autoamputation": The text introduces research that regards all extensions of ourselves as attempts by the body to maintain equilibrium against irritation. This process is described as a kind of self-amputation. The central nervous system protects itself from overstimulation by isolating or "amputating" the offending function. This theory explains "why man is impelled to extend various parts of his body by a kind of autoamputation".

The Wheel as an Example: The book uses the wheel as an example of this process. The pressure of new burdens led to the extension, or "'amputation,'" of the foot from the body into the form of the wheel. This amplification of a single function is made bearable only through a "numbness or blocking of perception".

etc