originally invisible ink (probably lemon or onion juice)

Ingredients

lemon juice, onion juice

Preparation Steps

Original Recipe Text

The secondary letter was written diagonally across the page using organic juices that were originally transparent or invisible (p. 130). This was a common technique for confidential correspondence.

Evidence

"It is written diagonally across the paper in originally invisible ink (probably lemon or onion juice)."

Remarks

The invisible ink resides beneath thick black letters of a main letter addressed by a female of high rank to 'Abd Allah Khan (p. 130). The visible main text is in black ink on buff paper with gold sprinkles (p. 130).