This short note tries to highlight an egregious error present in the diagrams of perfectly elastic demand and perfectly elastic supply in microeconomic textbooks. Both these diagrams are incomplete in most of the books as far as the second price is concerned. It should have been taken to show the infinite change in demand and supply, which is missing in the diagram. The subject having been accorded the status of science, this mistake needs to be rectified on an immediate basis, at least by teachers dealing with the instruction of microeconomics, for the purpose of maintaining academic purity and mathematical consistency in the treatment of this topic. I have presented the correct diagrams of perfectly elastic demand and supply along with the necessary mathematical explanation in the concluding part of this paper.

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