Viewport error when embedding PDF in HTML

I’m using the answer by batfan to this seemingly famous SO question: Recommended way to embed PDF in HTML?

I inserted the following into my HTML:

<embed src="/pdf/3" height="1600" width="1600" type="application/pdf">

This does not work as intended: The PDF title shows correctly and the viewer loads but no PDF is shown. When I inspect the blank PDF viewer I see the following error:

Uncaught TypeError: Cannot read property 'x' of undefined
    at Viewport.getPageInsetDimensions (viewport.js:1161)
    at Viewport.getPageScreenRect (viewport.js:1185)
    at PDFViewer.viewportChanged_ (pdf_viewer.js:1044)
    at Viewport.viewportChangedCallback_ (pdf_viewer.js:254)
    at Viewport.updateViewport_ (viewport.js:398)
    at Viewport.resize_ (viewport.js:425)
    at viewport.js:1149
    at Viewport.mightZoom_ (viewport.js:509)
    at Viewport.setDocumentDimensions (viewport.js:1138)
    at PDFViewer.setDocumentDimensions_ (pdf_viewer.js:1264)

Tested in Chrome and Firefox. Any idea?