I am trying to generate a PDF from Rmarkdown that includes external images (i.e., not figures generated from R code, which has been addressed in other questions, but images from other sources). The problem is that when I generate the PDF, the images don't appear where I placed them in the source code, but rather are moved around, presumably so as not to break the text. To my knowledge, this does not happen with figures generated from R code - those are placed immediately after the R code that generated them. Is there a way to fix this so that images are forced to appear in the text where I place them, as if they were generated from R code?
Some sample Rmd is below. If either of the two images is large, one or the other will be moved until after the text.
---
title: "Untitled"
author: "Me"
date: "December 16, 2016"
output: pdf_document
---
## One image with text
If any of the images are too large, they will be moved elsewhere.
First image goes here:

First image should be before here.
## Another image
Second image goes here:

Second image should be before here.