diff --git a/book.toml b/book.toml
index 31419fde8d..1a24b3cdcb 100644
--- a/book.toml
+++ b/book.toml
@@ -3,6 +3,8 @@ title = "The Rust Programming Language"
 authors = ["Steve Klabnik", "Carol Nichols", "Contributions from the Rust Community"]
 
 [output.html]
-additional-css = ["ferris.css", "theme/2018-edition.css"]
+additional-css = ["ferris.css", "theme/2018-edition.css", "theme/semantic-notes.css"]
 additional-js = ["ferris.js"]
 git-repository-url = "https://github.com/rust-lang/book"
+
+[preprocessor.trpl-note]
diff --git a/theme/semantic-notes.css b/theme/semantic-notes.css
new file mode 100644
index 0000000000..7e68eb371d
--- /dev/null
+++ b/theme/semantic-notes.css
@@ -0,0 +1,13 @@
+/*
+  This is copied directly from the styles for blockquotes, because notes were
+  historically rendered *as* blockquotes. This keeps the presentation of them
+  identical while updating the presentation.
+*/
+.note {
+    margin: 20px 0;
+    padding: 0 20px;
+    color: var(--fg);
+    background-color: var(--quote-bg);
+    border-block-start: 0.1em solid var(--quote-border);
+    border-block-end: 0.1em solid var(--quote-border);
+}
diff --git a/tools/src/bin/semantic-notes.rs b/tools/src/bin/semantic-notes.rs
new file mode 100644
index 0000000000..e69de29bb2